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The various monstrosities found throughout the world of Terraria, many of which are tied into game progress and the world's lore.
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Pre-Hardmode Bosses
King Slime
"The lord of all things slimy."
- Slimes normally aren't intelligent, but occasionally they merge together to become a powerful force to swallow all things.
- Ambiguous Situation: The ninja's significance to King Slime. While it may be a very recent victim, the fact that they don't show signs of being digested, as well as the repeated prominence of the Ninja in the trophy and achievement artwork implies they may be a symbiotic entity.
- And Your Reward Is Clothes: You beat it? Enjoy your random part(s) of the ninja costume and possibly the boss mask. Not so bad since 1.2.4 as it now drops the Slime Hook, the Slime Gun and a Slimy Saddle that you can get a Slime mount. Then 1.3 improves the drops even more by making the Ninja costume into functional armor that improves Throwing weapons.
- Asteroids Monster: It will eschew normal slimes from itself as it takes damage.
- Blob Monster: It's a giant Slime.
- Cool Crown: Now wears one after the 1.3 update, making it look very similar to King Slime from Dragon Quest.
- Flunky Boss: Spawns blue slimes as it takes damage. On Expert, it can also spawn spiked blue slimes.
- Harmless Enemy: In Expert Mode, it drops a Royal Gel that, when equipped, turns almost all slimes into these by making them passive.
- King Mook: Basically a bigger, stronger version of the blue Slime. After the 1.3 update he even has a crown, and also appears as the boss of a Slime Rain.
- Optional Boss: It isn't required for progression and, prior to 1.3, had fairly out of the way spawning requirements. However 1.3 downplayed this by having it more likely to spawn naturally as the end boss of the Slime Rain event and making its summoning item cheaper along with giving it more useful drops, though it’s still not required for progression.
- Shout-Out: To Ninja Gaiden with the ninja floating inside it, being a reference to a boss of the same one you fight.
- Shows Damage: It gets smaller as its health gets lower. Justified as it starts losing mass as it takes damage, as shown by the blue slimes it releases when taking enough damage.
- Spike Shooter: Not King Slime itself, but the Spiked Blue Slimes it spawns on Expert can fire spikes at the player.
- Teleportation: Will now dissolve and reform on the player if it happens to get stuck or manages to escape it for a while, so it cannot be trapped or outran anymore.
- Took a Level in Badass: Prior to 1.3 the boss was a joke and was easily cheesed by simply boxing it (or yourself) in note . After 1.3 it gained the ability to teleport, forcing you to face it, and it’s spawn, head on, making the boss a genuine threat early game.
The Eye of Cthulhu
"You feel an evil presence watching you..."
- A piece of Cthulhu ripped from his body centuries ago in a bloody war. It wanders the night seeking its host body… and revenge!
- The Berserker: In Expert Mode, when the Eye of Cthulhu is brought to low health, it will supplement its regular charges with an extremely fast zig-zagging charge. The lower its health, the more it does this; when on the verge of death, it will continuously make mad dashes in your general direction.
- Early-Bird Boss: After the player has satisfied a few relatively easy-to-meet conditions, the Eye of Cthulhu may simply decide to show up one night and start attacking, even if it hasn't been summoned. While it's still within reason to defeat it, it's also just as likely that the player lacks the equipment or skill necessary to fend it off.
- Eldritch Abomination: Well, at least the eye of one. Fittingly, it defies nature, although it's weak enough such that it can be slain even by somebody with a meagre bow or staff and a good enough running speed; it's a massive, disembodied, floating eye, for one, and it rips its iris open to reveal teeth once its health is lowered enough.
- Eye Scream: In its second phase, it tears itself open to reveal a sharp set of teeth.
- Faceless Eye: It used to be in Cthulhu's face, but it came flying out once the Dryads killed him, leaving it roaming the night killing whatever it comes upon.
- Final Boss Preview: For both Ocram, which shares its attack pattern, and the Moon Lord, who spawns True Eyes of Cthulhu.
- Flunky Boss: For the first phase, it shoots weaker and smaller Demon Eyes called Servants of Cthulhu at you.
- Giant Eye of Doom: The first major Lovecraftian horror most players with find themselves against, and once it loses enough health it ditches its iris for a horrifying and toothy mouth. With its speedy charge, it can easily outmatch an unprepared player.
- Guest Fighter: Also appears as a boss in Dungeon Defenders 2 as part of its crossover with Terraria. Similarly, it appears in Don't Starve Together under the name "Eye of Terror" alongside the Twins.
- King Mook: A bigger, badder version of the common Demon Eye enemy.
- Optional Boss: It doesn't drop anything needed for progression, but you're pointed in the direction of killing it anyway as it will usually be the first boss to spawn, either naturally or by finding and using a Suspicious Looking Eye underground.
- Time-Limit Boss: It will run away if you do not defeat it by dawn.
- Turns Red: Once at half health, it spins in a circle, releasing a small swarm of Demon Eyes and gaining a giant mouth where its iris was. In this state, it no longer shoots Demon Eyes but charges more aggressively. The 1.3 Big Update adds a new attack to the Eye's arsenal in Expert Mode, granting it a powerful and even faster berserker charge that it uses in proportion to how much damage it's taken.
- Warm-Up Boss: Eye of Cthulhu is the first progression-related boss in the game, and has relatively low health and a predictable pattern. As such, it serves to introduce the player to bosses in the game.
- Wake-Up Call Boss: For those who faced the King Slime earlier than anticipated.
- It also serves this role in Expert Mode, demonstrating that bosses have become much stronger than they were in normal mode. Its movement is upgraded to nearly match The Twins' ability to track the player's position, it releases a large swarm of lesser eyes transitioning into its second phase, and the new Desperation Attack it uses makes it extremely difficult for early-game characters to both hit and dodge the Eye of Cthulhu when it's on its last legs.
The Eater of Worlds
"Screams echo around you..."
- Conceived from the bottomless malice of the Corruption, this mighty abyssal worm tunnels wildly to devour all in its path.
- Asteroids Monster: If you destroy a segment that would leave two intact segments ahead or behind it, the detached segments will become a separate worm that must also be destroyed. At a bare minimum, you have to kill at least half of the Eater of Worlds to kill it permanently.
- Eldritch Abomination: A gigantic mutant worm with eyes all around it's body that heralds from the Corruption. If lore is any indication, it's entirely possible that the Eater of Worlds isn't a worm so much as Cthulhu's intestines.
- King Mook: To the Eaters of Souls and Devourers in the Corruption.
- Open-Ended Boss Battle: It (along with the Brain of Cthulhu) doesn't actually need to be defeated in order to progress the game: in addition to its main reward of Shadow Scales dropped upon death, each of its individual segments also have a chance of dropping a few, more than enough to collect the six required to forge the Nightmare Pickaxe, at which point you can flee the battle or die (on anything other than Hardcore) without having to worry about finishing the job. However on Expert and above, killing it rewards the highly useful Worm Scarf (which grants a flat 17% damage reduction)
- Sand Worm: Well, Corruption Worm. Plays this straight if summoned in a Corrupted desert.
- Super Spit: The Expert Mode version of the Eater of Worlds possesses the ability to shoot Vile Spit like a Corruptor on LSD.
- Segmented Serpent: Each of its segments is its own entity with its own health bar, and are capable of acting as independent worms so long as two segments are connected.
- Skippable Boss: If you can fish up the Reaver Shark, you can skip the Eater of Worlds. It'll be a bit harder to mine Hellstone with inferior armor, but not insurmountable (unless you farm Eater of Souls instead for the Ancient variety of Shadow Armor).
- Averted as of Journey's End, where the Reaver Shark has been nerfed and the Nightmare Pickaxe and its counterpart are now required to mine Hellstone, meaning you will have to face the Eater of Worlds at least once to progress (even if you don't necessarily have to beat it, as seen above).
Brain of Cthulhu
"A horrible chill goes down your spine..."
- A piece of Cthulhu torn asunder, this vile mastermind pulses with agony and aids the Crimson to an attempt to avenge its master.
- Bizarre Alien Biology: It has a heart inside of it. With an eye on it.
- Brain Monster: A giant, monstrous brain which attacks you in the Crimson should you smash too many Crimson hearts or use a bloody spine to summon it.
- Doppelgänger Spin: On Expert, during the second half of the fight. Each time it teleports, it produces three translucent, harmless fake images of itself that also converge on you. As its health gets lower, these images become less transparent, making it harder to distinguish the real one.
- Eldritch Abomination: Again, at least the brain of one.
- Flunky Boss: Much like the Eye of Cthulhu, it summons eyeball-like minions to attack you. Unlike the Eye of Cthulhu, these must be destroyed if you want to hurt the Brain itself.
- Open-Ended Boss Battle: It (along with the Eater of Worlds) doesn't actually need to be defeated in order to progress the game: in addition to its main reward of Tissue Samples dropped upon death, every Creeper it spawns also has a chance of dropping a few, more than enough to collect the six required to forge the Deathbringer Pickaxe, at which point you can flee the battle or die (on anything other than Hardcore) without having to worry about finishing the job. However, like the Eater of Worlds, killing it on Expert or above awards the very useful Brain of Confusion (a 1/6 percent chance to dodge damage, with a buff to critical chance and enemies being confused given upon a dodge).
- Skippable Boss: If you can fish up the Reaver Shark, you can skip the Brain of Cthulhu. It'll be certainly a bit harder to mine Hellstone with inferior armor, but not insurmountable.
- Averted as of Journey's End, where the Reaver Shark has been nerfed and the Deathbringer Pickaxe and its counterpart are now required to mine Hellstone, meaning you will have to face the Brain of Cthulhu at least once to progress (even if you don't necessarily have to beat it, as seen above).
- Status Infliction Attack: On Expert, any Collision Damage with the eyeballs or the Brain can cause the Confused, Poison, Bleeding, Darkness, Broken Armor, or Weak status effects.
- Suspiciously Similar Substitute: Due to being a floating brain-like enemy that attacks you with eyeball-like minions, the Brain of Cthulhu is possibly the closest thing the PC version has to Ocram.
- Teleport Spam: In the second half of the fight.
- Villain Team-Up: According to its Bestiary description, the Brain is not directly related to the Crimson, but simply formed an alliance with it; It defends the Crimson's hearts and aids in its spread to avenge its originator's defeat.
- Weaponized Teleportation: The Brain's main attack is to teleport right on top of the player. To compensate for this, it's also the only boss that is susceptible to knockback.
Queen Bee
"The matriarch of jungle hives..."
- This highly aggressive monstrosity responds violently when her larva is disturbed, the honey-laden hives are her home turf.
- Bee Afraid: You stumble into a hive, with not many monsters inside unless you start digging into the walls. Then you attack the larva... and a gigantic bee attacks you furiously in retaliation.
- Bee-Bee Gun: Can send out smaller bees to attack you. When beaten, all the weapons received from her will spawn homing bees to attack the enemy. The Hive Pack that she drops on Expert Mode will strengthen half of said bees as well.
- Body Horror: She’s equal parts bee and beehive, judging from the holes in her abdomen and her ability to shoot bees at the player from them.
- Beware My Stinger Tail: Like the Hornets, she can fire out venomous stingers that poison the player.
- Big Creepy-Crawlies: The largest insectoid enemy in the gamenote .
- Berserk Button: Killing the Bee Larva in any of the bee hives will summon her.
- Boss Arena Recovery: Due to how the Queen Bee is summoned, you'll probably be fighting her inside a beehive, the bottom of which is lined with honey that you can take a dip in to recover health over time.
- Flunky Boss: One of her attacks is to release a swarm of tiny bees that follow you relentlessly.
- Glass Cannon: The bees she spawns have very little health, but they pack quite a wallop.
- Insect Queen: It's right there in the name.
- King Mook: A Queen Mook towards the Hornet enemies.
- Mama Bear: Kill her larva and she'll awaken and attack you in retaliation.
- Ramming Always Works: One of her attacks. She's able to fire out bees and stingers, but will also charge the player.
- Skippable Boss: Like the King Slime, there's no particular need to fight the Queen Bee unless you want her loot and the Witch Doctor NPC.
- Spam Attack: In Expert, her attacks get faster she nears death. This can lead to her chaining up charge attacks, or releasing swarms of bees followed by machine gun-like stinger barrages.
- Status Infliction Attack: Can poison you with her stingers.
- Time-Limit Boss: Averted, unlike many other bosses in the game.
- Turns Red: Only on Expert. Her attack pattern gets faster and more frequent as she loses health. In addition, her defense gradually increases as she takes damage on Expert, culminating in more than double her defense at critical health.
Skeletron
"The cursed guardian of the dungeon..."
- The disembodied bones of a former tyrant pulsed with a hatred so strong, it left behind a mighty curse which guards the dungeon.
- Beef Gate: He can be summoned as early as the first night but if you aren’t able to beat him, then you stand very little chance of surviving the dungeon.
- Cognizant Limbs: Both his hands. It's recommended to destroy them first, as they are his main means of attack. It's almost required to kill them first in Expert, because his head will have 100 defense until you do.
- Cycle of Hurting: On Expert, his spinning move upgrades once both arms are destroyed, becoming faster so he can stick to your character for continuous, huge Collision Damage.
- Dem Bones: It's a floating skull with disembodied skeletal arms.
- Dungeon Bypass: Very strongly averted. Try to tunnel past Skeletron and you'll be killed by the Dungeon Guardian, a Nigh-Invulnerable Beef Gate meant to punish such an attempted bypass. Even if you decide not to enter the dungeon at all, he is still required to be defeated if you want the cultists to appear and trigger the Lunar Events.
- Homing Projectile: In Expert, he fires homing skulls a la the Book of Skulls once you've destroyed one of his hands.
- Name-Tron: It's named Skeletron, although it's not a robot or machine at all.
- Skippable Boss: Subverted. He may seem completely optional, albeit at the cost of losing out on all of the very powerful pre-hardmode and post-Planter loot, along with both the Clothier and Mechanic, but killing him is required to spawn the cultists who initiate the endgame.
- Spectacular Spinning: For the player, anyway. His defense drops when his head is spinning.
- Time-Limit Boss: It will kill you if you do not defeat it by dawn.
- Turns Red: At dawn, it transforms into the Dungeon Guardian and will One-Hit Kill you. In Expert, once his hands are destroyed, he begins firing skulls at the player while also upgrading his spinning attack to perform a Cycle of Hurting.
- Undead Abomination: It's a giant, skeletal monster that, according to the lore, is made of a part of Cthulhu's skeleton itself.
Dungeon Guardian
- A lethal sentry that stands watch over the Dungeon's gates. Those who are deemed unworthy to enter shall not pass!
- Bragging Rights Reward: The Bone Key
it drops when killed, which summons a mini-Skeletron pet. - Dem Bones: A flying skull.
- Doppelgänger Attack: The game treats it as a normal enemy, not a boss, so it is possible for more than one to spawn. It's not uncommon for two to chase you out of the dungeon. Death is pretty much assured when this happens.
- Implacable Man: It can phase through structures and the ground so walling it up is a no-go, it will chase you across the map and won't stop coming until either it despawns (which barring an endgame mount fast enough to outpace the creature would require an absolute miracle), it hunts down and kills you, or you manage to kill it. It's immune to knockback and will shrug off everything up to and including the most powerful weapons in the game without slowing down one bit. Your only advantage over it in the end is agility.
- The Juggernaut: Doesn't stop homing in on you, takes Scratch Damage from everything, One Hit Kills you, and is practically invulnerable to knockback.
- Lightning Bruiser: It can fly faster than anything short of the best mount in the game, has 9999 HP and takes 1 damage from everything, and can One-Hit Kill an endgame melee tank build on contact.
- Lord British Postulate: It originally had 9999 hp, 9999 defense and 9999 damage, aside from being very fast. Yet, many players were able to kill it, using fast shooting weapons (that would deal 1 damage per hit) and reversing gravity in order to be fast enough not to be hit. Thanks to how defense works, and the addition of armor dealing melee damage done to the player back to the attacker, as well as an item allowing a small dodge chance, this was in a few updates relatively easy, until it was patched by decreasing the guardian's attack to 1000.
- Marathon Boss: You have to run away from it dealing Scratch Damage until its health depletes, which can take quite a long time. The absolute fastest you can kill the Guardian is in about five minutes, with the right equipment, and that's on Normal mode.
- Nigh-Invulnerable: It has 9999 HP (which is doubled in Expert Mode) and 9999 Defense (turning all attacks into Scratch Damage), and is Immune to Flinching. It can be killed, but only with a lot of preparation.
- One-Hit Kill: Its sole purpose of existence. With an attack that deals 1000 damage, if it catches you, you're dead.
- Only the Worthy May Pass: Its Bestiary entry outright states it will not allow anyone deemed unworthy to pass into the dungeon.
- Permanently Missable Content: Vanishes once Skeletron is defeated, so get your Bone Key before you open the dungeon.
- Ramming Always Works: It will crash into you at high speed and make you explode into gibs on impact.
- Rasputinian Death: Pretty much required to kill it. In fact, it's likely that the reason why it blinks out of existence when it finally kicks the bucket is because in the process of killing it you have to grind up the creature until nothing remains.
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Self-Imposed Challenge: Killing it is considered a personal achievement by Terraria veterans. The devs have acknowledged this, and it now drops the aforementioned Bone Key as a reward. - Spectacular Spinning: Constantly in this state.
Deerclops
- Hailing from a distant land, this cyclopic monstrosity lurks in cold places, wreaking havoc on those who disturb it.
- Adaptational Badass: The Deerclops was no slouch in its source game, but Terraria gives it a slew of new attacks besides its icy Ground Punch, such as throwing a barrage of snow projectiles into the air and even summoning the Night Hands from its source game.
- Anti-Escape Mechanism: It forces the player into combat range by becoming invulnerable to damage if it's too far, as well as casting a slow debuff onto the player.
- Casting a Shadow: Its insanity aura is presented as having Night Hands pop up near it before charging at the player, and it can also turn into an invulnerable shadow of itself if it's too far from the player.
- Duel Boss: An update causes it to take up most of the allotted spawn slots for enemies near the player, meaning Deerclops is the only threat you need to really prioritize.
- Guest Fighter: Originates from Don't Starve.
- Hitbox Dissonance: The collision hitbox that determines if Deerclops does contact damage to you only covers the waist-up. You can run between his legs and make it out the other side unscathed provided he doesn't catch you with a different attack.
- Plot-Irrelevant Villain: Doesn't have anything to do with the overarching plot of the game.
- Victor Gains Loser's Powers: Combined with Defeat Equals Friendship with the Expert Mode-exclusive Bone Helm accessory, which passively summons the Night Hands to protect you from any nearby foes when worn.
Wall of Flesh
"The master and core of the world..."
- Serving as the world's core and guardian, the towering demon lord exists to keep powerful ancient spirits sealed away.
- Advancing Boss of Doom: It will charge at you and pursue you from one end of the world to another, there is no way to get past it, and if it is still alive by the time it is on the other end, it will crush you to death.
- Barrier Maiden: As eldritch and frightening as it is, lore states that the Wall of Flesh is the world's guardian, holding back the spirits of light and darkness. Destroying the Wall releases the spirits to expedite the process of finding a new one, with devastating effects on the land itself.
- Beef Gate: Almost literally in this case. Fighting the Wall of Flesh requires being able to survive in the most dangerous Pre-Hardmode biome well enough to fight a boss that chases you through it and almost requires the best Pre-Hardmode weapons, armor, and accessories to beat. Given the massive Difficulty Spike he guards, it serves to make sure you are capable of surviving early Hardmode.
- Breath Weapon: A particularly disgusting version. When it’s health has been cut down to a certain point it will start vomiting swarms of Leeches at the player.
- Body Horror: As its name suggests, it's a giant wall of viscera with stringy tentacles, two enormous bulging, veiny eyes, and a gaping, protruding mouth. The fact that it also spews out Leeches, which are noted in the bestiary to be parasitic creatures full of the monster’s healing blood, doesn’t imply anything healthy about the insides of the beast either.
- Dark Is Not Evil: Despite being an enormous wall of meat that resides in Hell and is described as being a demon lord, the Wall of Flesh's purpose is actually to contain the greater part of the Corruption/Crimson and the pretty-but-no-less-dangerous sprites of the Hallow. Slaying it unleashes them; unless you've taken preemptive measures to limit the spread of these biomes, you will quickly learn why they were locked up to begin with.
- Disc-One Final Boss: The most powerful pre-hardmode boss you face before you go into hardmode.
- Eye Beams: It fires volleys of purple lasers at you from its eyes, and the time between shots decreases as its health gets lower until it's full-on Beam Spam.
- Eldritch Abomination: Moreso than the other pre-hardmode bosses because it can inflict a Mind Rape on you that forces you to kill it to survive. According to a card, it's the lord of eternal nightmares. And when killed, the world gets drastically and irrevocably changed.
- Flunky Boss: This game loves these bosses a lot. The Wall of Flesh has a number of flunkies called The Hungry attached to it which reach out to damage you before detaching and flying at you upon death. It can also summon burrowing Leeches.
- Gasshole: It will periodically burp out leeches as one of its attacks.
- Go for the Eye: While both its mouth and eyes are vulnerable, the eyes have zero defense and thus do not benefit from any Damage Reduction, making them the preferred targets.
- Immune to Flinching: Surprisingly, no, despite being an Advancing Boss of Doom. Shooting Heart Arrows at its mouth will actually stun it for a brief while.
- Living Structure Monster: The Wall of Flesh is Exactly What It Says on the Tin — a massive, moving wall of meat with eyes and a mouth.
- Load-Bearing Boss: Its death infects the world with large swathes of ever-expanding Hallow and Corruption.
- Marathon Boss: Clocks in at 8000 HP in normal mode, which is considerably higher than any other easymode boss. Even top-tier easymode weapons will take a while whittling this guy down.
- Shout-Out: According to Redigit, it was inspired by the Demon Wall bosses in the Final Fantasy series.
- Supernatural Fear Inducer: It's the only enemy in the game that can inflict the "Horrified" debuff on your player, which results in death if you attempt to escape using a teleportation item like the Recall Potion or Magic Mirror. The tooltip for this debuff is "You have seen something nasty, there is no escape".
- Time-Limit Boss: You have to defeat it before it reaches the other side of the world and kills you.
- Turns Red: As you wear down its health, it will start gaining speed, belch up leeches more often and will shoot its Eye Beams more often. On Expert, he gains a massive burst of speed when at critical health.
- You Will Not Evade Me: The wall will use its tongue to reel you in if you run too far from it, get behind it or try to escape the underworld conventionally. Trying to use the magic mirror to escape splatters you when you reach your spawn. This isn't as bad as it sounds for soft-core or even medium-core characters as your money/items drop at the spawn/bed that you warped to. Hard-core however...this happens.
Hardmode Bosses
Queen Slime
- Hallowed slimes consolidated into a haughty, crushing force adorned in dazzling crystals. She is rumored to grow wings.
- Blob Monster: Much like King Slime, Queen Slime is a giant Slime.
- Cool Crown: Just like King Slime, Queen Slime wears a crown on the top of her head.
- Distaff Counterpart: To King Slime, of course. Nearly all of her loot (a set of crystalline ninja armor, a saddle that summons a winged slime mount, a method of coating others in harmless goo, and a unique grappling hook) is some sort of upgrade to King Slime's loot.
- King Mook: She's a Queen Mook to Slime enemies.
- Mook Maker: Like her counterpart, Queen Slime summons Slime minions as she takes damage, bringing spiky Crystal Slimes, bubbling Bouncy Slimes, and winged Heavenly Slimes to her side as the fight progresses.
- Optional Boss: One of three Hardmode bosses that aren't needed to progress the game.
- Pink Means Feminine: It befits her nature as both a queen and a creature of the Hallow.
- Turns Red: At 50% health, Queen Slime sprouts feathery wings and takes to the skies, mixing up her tactics as she does so.
- You Will Not Evade Me: Like King Slime, she can teleport. Her second phase grows wings and flies after you.
The Twins
- Belonging to a pair of mechanically-recreated Eyes of Cthulhu, this one focuses its energy into firing powerful lasers. (Retinazer)
Belonging to a pair of mechanically-recreated Eyes of Cthulhu, this one chases at high speeds, exhaling cursed flames. (Spazmatism)
- Artificial Limbs: The Mechanic was forced to build them so they could serve as Cthulhu's new eyes.
- Breath Weapon: Spazmatism will spew a constant stream of Cursed Flames in its second phase, though at least the range is limited.
- Beam Spam: The lower Retinazer's health is in the second phase, the more it does so. At critical health it can fire as fast as a Megashark.
- Degraded Boss: In a rare beneficial version! Players can craft an staff that lets them summon miniature stage two Twins to aid them in battle and they keep their signature breath and laser attacks. A properly geared player can have a pack of 22 of these things trailing behind them.
- Dual Boss: Thought the Eye of Cthulhu was fun? Now you get to fight two of them at once, one packing Eye Beams and the other with a Breath Weapon. Have fun!
- Essence Drop: Drop Souls of Sight when the remaining one is destroyed.
- Eye Beams: Retinazer, Retinazer, Retinazer. It gets worse the lowers its health gets. Spazmatism's fireballs in its first phase also count on a technicality.
- Eye Scream: Downplayed. Like the Eye of Cthulhu, they break their irises open upon reaching half health. However, this is where their true, mechanical nature is revealed, making it less so that they are eyes tearing themselves apart to get a combat advantage and more that they are eye-shaped machines tearing themselves apart to get a combat advantage.
- Faceless Eye: Two of them this time, but mechanically enhanced. Though they are designed to fit back into Cthulhu's sockets in his cybernetically revived form.
- Fusion Dance: In the "Get Fixed Boi" seed, the Twins combine with the other Mechanical Bosses to form Mechdusa.
- Giant Eye of Doom: Much like the Eye of Cthulhu, except now there's two of them!
- Hellfire: Spazmatism uses Cursed Flames as its ranged attacks.
- Mechanical Abomination: The mechanical reincarnation of the Eye Of Cthulhu.
- Punny Name: Both of their Portmanteau names are eye puns.
- The retina is the part of the eye where light is focused, and a laser is a focused beam of light. Retinazer attacks with focused Beam Spam.
- A 'spaz' is a person who acts chaotically and jerkily, while astigmatism is an eye problem causing blurry vision. Spazmatism jerkily charges all over the place and clouds its own vision with flames.
- Robotic Reveal: Unlike the other mechanical bosses, these two appear to be biological at first. Once you get their health down far enough, however, they enter their second phase, shedding their organic tissue and unveiling themselves as completely-robotic recreations of the Eye of Cthulhu.
- Short Range Guy, Long Range Guy: Apparent in their second forms—Spazmatism is the Short Range, attempting to stay close to breathe cursed flames and charge the player, while Retinazer is the Long Range, attempting to stay far while firing lasers at the player.
- Technicolor Eyes: Retinazer's iris is red, and Spazmatism's is green, appropriate for the latter since it spews green fire. Both have blue pupils.
- Time-Limit Boss: The two will run away at dawn.
- Turns Red: Like the Eye of Cthulhu, the Twins will enter a second form when low enough on health.
- Spazmatism's charges become much faster and more frequent, and while it's not charging, it relentlessly pursues the player while breathing a constant stream of Cursed Flames.
- Retinazer switches from blue lasers to more damaging red lasers, and the lower its health gets during its second phase, the faster it fires the laser cannon, until it's essentially Beam Spam.
The Destroyer
"You feel vibrations from deep below..."
- A mechanical simulacrum of Cthulhu's spine decorated in laser-armed probes, which detach from its body when damaged.
- Achilles' Heel:
- The Destroyer's massive, segmented body make it highly vulnerable to piercing weapons.
- Unlike the other mechanical bosses, the Destroyer is stuck to the ground. Standing on a platform high enough in the air will make it hard for the Destroyer to even get to you, barring its lasers and Probes.
- Animal Mecha: A giant metal worm.
- Anti-Frustration Features: While most worm-type enemies' drops will spawn from their head segments when they die, the Destroyer's drops will instead spawn at the segment closest to the player on death, as its massive size makes it very easy to lose track of where the head was when you killed it.
- Artificial Limbs: The Mechanic was forced to build it so it could serve as a replacement backbone for Cthulhu.
- Attack Drone: Sends these out which pepper you with lasers. Thankfully, they drop hearts and mana stars.
- Attack Its Weak Point: Unlike the rest of its body, the Destroyer's head has 0 defense. As it attacks by lunging at you, you'll have plenty of opportunities to strike it.
- Beam Spam: Both its sections and probes can do this from time to time.
- Boss Arena Recovery: Destroying the probes it sends out will get at least one heart and/or a mana star if you've been using magic weapons.
- Collision Damage: Notably, on Expert and Master, the Destroyer's head making contact with you deals more damage than any other attack save for the Phantasmal Deathray and anything from daylight Empress of Light.
- Composite Character: While it's mostly based on the Eater of Worlds, the eyeball-like Probes it sends out resemble the Brain of Cthulhu's Creeper minions.
- Contractual Boss Immunity: Unlike any other enemy in the game, the Destroyer is completely immune to all debuffs.
- Damage-Sponge Boss: Has more HP than any other non-composite entity opponent in the entire game at a whopping 80000 (120000 in Expert), but since all of its segments are individual targets vulnerable to attack, piercing and melee weapons will rack up massive amounts of damage by striking multiple segments on each pass, balancing out the extra health.
- Energy Weapon: The aformentioned probes will start letting out a barrage of lasers should they be allowed to survive for a bit.
- Essence Drop: Drop Souls of Might when destroyed.
- Flunky Boss: The probes it sends out upon being hurt.
- Fusion Dance: In the "Get Fixed Boi" seed, the Destroyer combines with the other Mechanical Bosses to form Mechdusa.
- Sand Worm: A robot sand worm, at that.
- Segmented Serpent: The Destroyer possesses 82 separate segments, each of which is as long as your character is tall, making it undisputably the biggest thing in the game. The player can attack multiple segments at one go, allowing them to deplete its massive HP faster. If someone has already defeated The Twins and has used their souls of sight to build a Magical Harpnote weapon, the boss fight becomes nearly effortless.
- Super-Persistent Predator: Unlike most bosses, the Destroyer will not despawn if you get too far away from it, and will pursue you across the world if it has to.
- Time-Limit Boss: Runs away at dawn.
Skeletron Prime
"The air is getting colder around you..."
- Mechanically reconstructed for reviving Cthulhu, this Skeletron has more arms than ever before, and a variety of fierce weapons.
- Artificial Limbs: The Mechanic was forced to build it so it could serve as Cthulhu's new skeleton.
- Arm Cannon: One of his arms has a cannon that functions like a Grenade Launcher, lobbing bombs at the player that explode after a short delay.
- Armored But Frail: Downplayed. Of the Mechanical bosses, Skeletron Prime has the most defense, but in terms of health he's only beating out the Twins individually.
- Chainsaw Good: The Prime Saw arm.
- Cognizant Limbs: Has four destructible limbs, each carrying a deadly weapon of its own.
- Crippling Overspecialization: The Prime Cannon arm fires bombs which explode on contact with solid platforms. This means that a floating arena of wooden platforms makes the arm utterly incapable of causing anything other than Collision Damage. However, note that this is no longer true as of 1.4.01 onwards, meaning in Expert Mode, he can and will wreck your arena.
- Dem Bones: Mechanical ones this time.
- Energy Weapon: The Prime Laser arm.
- Essence Drop: Drop Souls of Fright when destroyed.
- Evil Is Deathly Cold: The warning message that appears to indicate that it will spawn on a Hardmode night is "The air is getting colder around you", implying this trope. Downplayed in that it lacks any sort of ice or cold-themed attacks.
- Fusion Dance: In the "Get Fixed Boi" seed, Skeletron Prime combines with the other Mechanical Bosses to form Mechdusa. Prime is the binding agent between the three; if you kill Skeletron Prime before one of the other components of the boss, they'll resume their usual behaviour.
- Jet Pack: While the head floats, Skeletron Prime's arms seem to move using jets of (harmless) flame.
- Marathon Boss: With its four arms and high HP, Prime can easily drag the fight out until morning if the player's damage output is too low, and unlike the Destroyer, it isn't made up of hundreds of segments that can all be targeted.
- Mechanical Abomination: The mechanized reincarnation of the Skeletron.
- Multi-Armed and Dangerous: Has four arms as compared to Skeletron's two, and each arm has a different weapon to murder you with on the end.
- Name-Tron: It's named Skeletron Prime. Unlike Skeletron, this one is mechanical.
- Power Pincers: The Prime Vice arm.
- SkeleBot 9000: It's a mechanical skull with four arms.
- Spectacular Spinning: Unlike Skeletron, Prime benefits from spinning as its defense actually increases instead of decreasing when it does so.
- Spikes of Doom: The head grows these when spinning.
- Throw Down the Bomblet: The Prime Cannon arm.
- Time-Limit Boss: Like Skeletron, Prime has a Dungeon Guardian form and will kill you at dawn.
Ocram
- Bait-and-Switch: The "Get Fixed Boi" seed features an item called "Ocram's Razor". One would think that the monster has finally returned, but it just summons Mechdusa.
- Beam Spam: Its first form loves this. Its second form basically pumps out laser shotgun blasts at the speed of a machinegun.
- Bullet Hell: During his second phase, he will be spraying countless laser blasts and Demon Scythes at a ridiculous speed. Not only does it do this itself, but this is also the focus of most strategies for fighting him.
- Call-Back: Oddly enough, to the Eye of Cthulhu. His strategy is similar, his flunkies are called "Servants of Ocram" like the Eye's "Servants of Cthulhu", and they share a battle theme.
- Eldritch Abomination: Quite. His appearance is extremely otherworldly even in comparison to the likes of the Celestial Pillars and the Moon Lord.
- Essence Drop: Drops Souls of Blight when slain, which are required to craft the end-game armors.
-
Exiled from Continuity: Word of God has stated that Ocram will never appear in any version of the game still recieving updates, although mods are fair game. The Labor of Love throws a few name drops his way, though. - Final Boss: Confirmed to be as such by the (console version's) developers. Subverted in the newer console version and the mobile version, as he was removed in the 1.3 update, which added the game's real final boss.
- Flunky Boss: Sends out Servants of Ocram, though he has plenty of other attacks. They're fairly easy to kill if you use Crystal Bullets. However, don't mistake him for relying solely upon them.
- Giant Space Flea from Nowhere: Has no buildup or references, not even in the item used to summon him.
- Lightning Bruiser: He moves fast and hits HARD.
- Nintendo Hard: He's pretty much impossible to kill without near-endgame to endgame armor.
- Omnicidal Maniac: If you summon it too close to your house/town, it can and will kill your NPCs.
- Sdrawkcab Name: "Ocram" is "Marco" backward, the name of Ocram's programmer.
- Turns Red: His second form turns out his eyes, reveals a bigger eye, and also amps up the power of his Beam Spam attack while allowing him to launch Blinding Demon Scythes.
Plantera
"The jungle grows restless..."
- A dormant, yet powerful floral guardian awoken by the fallout of Cthulhu's destroyed machinations. Its reach spans the entire jungle.
- Autobots, Rock Out!: Unlike every other boss, Plantera's theme is a heavy guitar-laden piece. It also doubles as a Boss Remix of the Jungle theme!
- Berserk Button: If you lure it out of the Underground Jungle biome, it will become more aggressive and damaging. She’s also not too amused about anyone breaking her bulbs either, as she’ll immediately awaken and begin hunting any players nearby upon someone doing so.
- Botanical Abomination: Implied. Plantera only awakens after the Mechanical Bosses are defeated, and it's somehow linked to biome spreading, as defeating it will slow the spreading down.
- Combat Tentacles: Its invulnerable grappling hooks can deal damage, and it sprouts a bunch of smaller, destructible ones when it Turns Red. In Expert Mode, its grappling hooks sprout them too when it Turns Red!
- Flunky Boss: The plants that it sprouts when it Turns Red.
- Foul Flower: Its initial form is a giant, aggressive flower bud. In the second phase, it drops off its flower and becomes a full-fledged Man-Eating Plant.
- Homing Projectile: Its second form launches Spores that will seek out and damage the nearest player.
- Impossible Item Drop: Plantera is a particularly strange case. Whereas most bosses can also drop some sort of item or weapon, most of them are somehow based on the abilities of the boss itself (e.g. the Book of Skulls fires the same skulls that Skeletron does in Expert Mode)... but what is Plantera doing with an electric guitar?note
- Man-Eating Plant: Even more so than the Man Eaters you used to encounter in the jungle.
- Pun: Of the band Pantera, especially so because of its unique boss theme.
- Rush Boss: Plantera's HP isn't too impressive compared to the mechanical bosses, who all have higher aggregate HP than it. However, what it lacks in durability it makes up for with heavy-hitting, hard-to-dodge attacks, especially since you're going to be fighting it in the cramped Underground Jungle or else.
- Samus Is a Girl: According to Cenx, Plantera is female.
- Silent Antagonist: Unlike most other bestial bosses, she doesn't make the standard roar you hear upon summoning a boss.
- Spike Balls of Doom: Spits these out in its first phase.
- Spike Shooter: First phase uses these. The rate of its fire increases as it loses health.
- Turns Red: At half health, the flower will drop off and sprout tentacle plants, and it'll become much faster and damaging.
- Wake-Up Call Boss: Plantera is significantly harder than the Mechanical Bosses, and a large amount of preparation is needed to even stand a chance of killing it, especially since its bulb appears at complete random. You can't lure it above-ground without it becoming much meaner, so if you do build an arena, you have to carve it out of the Underground Jungle while under attack by the monsters there.
Empress of Light
"A beautiful bullet hell."
- Beneath the Hallow's cleansing blanket lies a vengeful fae goddess bent on scrubbing the land of any and all impurity.
- Amazing Technicolor Population: Her skin is yellow.
- Blue-and-Orange Morality: She believes that killing a specific Hallowed butterfly, even by accident, warrants death, yet she is nowhere to be seen when it comes to infections/invasions of the Corruption, Crimson, the Celestial Pillars, or the Moon Lord. Unless the player summons her near those biomes, events, or while fighting the Moon Lord. But by killing that same butterfly and making her fight the player instead of any of them.
- Bullet Hell: Oh yeah. She practically floods the screen with projectiles. Cenx even described her fight as a "beautiful bullet hell" before the update's release.
- Dynamic Entry: Appears in an aurora of rainbow-colored light. If fought at day, the aurora will be yellow instead.
- Everything's Better with Rainbows: Well, worse for the player, but all of her attacks glow brightly are colored in every color of the rainbow. She even appears in a rainbow-colored aurora when spawning. However, if she's fought in the day, all of her rainbow-colored attacks will turn bright yellow to signify that the player is now in serious trouble.
- The Fair Folk: She is a fae goddess who, like the rest of the Hallow, is a vicious Knight Templar with a desire to purge the land of any and all impurity.
- Light 'em Up: She's the empress of the stuff. All of her many attacks are themed around light and rainbows, and she's vastly empowered during the day.
- Light Is Not Good: Just like the rest of the Hallow, she is obsessed with destroying any sort of impurity. Granted, to summon her you have to kill an extremely rare butterfly, yet the bestiary entry for said butterfly explicitly describes her as a tyrant...
- Lightning Bruiser: She has 70,000 HP at minimum which can go up to 124,950 on Master - significantly more than her fellow Optional Boss Duke Fishron, who has 50,000 to 76,500 HP respectively. She also flies around the air quickly, and hits extremely hard with both projectiles and contact damage.
- Ms. Fanservice: Her armor is revealing and due to her size her sprite is much more detailed than the NPCs or humanoid monsters.
- No-Damage Run: Obtaining the Terraprisma requires the Empress to be defeated while doing all of the damage during the day. Because every hit is a One-Hit Kill at day, this is a given.
- Nonstandard Character Design: Outside of the Lunatic Cultist, she's the most humanoid non-event boss, resembling the Ice Queen.
- One-Hit Kill: Fighting her in the day causes all her attacks to deal at least 10,000 damage.
- Physical Goddess: Is explicitly described as a goddess in the bestiary, and given just how much of a powerhouse she is even without her daytime boost, there’s not much evidence to dispute that.
- Sinister Schnoz: According to Crowno, the game's artist, the v-shaped line on her face is not her mouth, but her nose. It's a rather pointy nose for a tyrannical ruler of the Hallow.
- Superboss: Like Duke Fishron, she is completely optional and not required to face the Final Boss, and you likely have to go out of your way to summon her, although unlike Duke Fishron she can be accidentally summoned if you're supremely unlucky. And she demands respect, too - despite being able to be summoned right after Plantera, she's so incredibly difficult and unorthodox compared to every other boss in the game (arguably including the Final Boss) that gear obtained from the Lunar Events, or gear obtained after Golem or even Duke Fishron is heavily encouraged to be acquired first. Yet if you do kill her, she can drop some incredibly good gear for your troubles, which will make all of the remaining challenges in the game significantly easier.
- There Is No Kill Like Overkill: Fighting her in the day causes her attacks to deal at least 10,000 damage to you. You have a maximum of 500-600 HP.
- Time-Limit Boss: Like Skeletron and Skeletron Prime before her, once the sun comes up, the Empress's attacks will kill you instantly. If summoned during the day (likely by a player looking for her Bragging Rights Reward), she will run away at dusk if she and the player are (somehow) both still alive by then.
- Turns Red: Once she gets below half HP, she'll vanish momentarily, before switching her attack pattern for an improved variation and launching attacks even faster than before.
- Like Skeletron Prime, fighting her in the sun makes her attacks nearly impossible to survive, dealing a minimum of 10,000 damage. Unlike Skeletron Prime, managing to defeat her during the day (no damage can be done at night for this to work) nets you a unique weapon, the Terraprisma.
Golem
"The stone-faced ritualistic idol of the lihzahrdian tribe..."
- A remarkable display of ingenuity constructed by the Lihzahrd clan. Powered by solar energy cells, it is ready to guard the temple.
- Berserk Button: If you lure him out of the Underground Jungle biome, he will become more aggressive and damaging.
- Cognizant Limbs: His arms can be attacked and destroyed separately, though this isn't necessary to beat him.
- Detachment Combat: When his health gets low, his head separates from his body and attacks separately, although the head cannot be damaged.
- Eye Beams: The first phase uses these when its health gets low. The head in the second phase also uses them.
- Fireballs: Spits out bouncing ones.
- Golem: Duh. It's a construct created by the Lihzarhd.
- Hyper-Destructive Bouncing Ball: The fireballs the head shoots out.
- Losing Your Head: When he Turns Red. Justified because he's a construct. Said head is also invulnerable to damage during the second phase.
- Outside-the-Box Tactic: The Golem used to be one of two bosses unable to pass through solid blocks, allowing a player to trap him inside and attack him from there with a wall-piercing weapon.
- Power of the Sun: Many of the Golem's drops are associated with daytime and the sun.
- Rocket Punch: His arms. The Golem Fist he drops allows the player to do the same.
- Slow Laser: The Eye Beams it fires are slower than light.
- Took a Level in Badass: Prior to 1.4.4 it was a notoriously easy boss. In said update it received a massive buff to it’s attacks, it’s fists can no longer be deflected ([[Discard and Draw though they now need to charge up), and various other tweaks were made that make it a much greater threat.
- Turns Red: Its head flies into the air and becomes invincible when its health is depleted, forcing you to attack its body directly.
Duke Fishron
"The mutant terror of the sea."
- An aquatic pigron mutation from the depths of the ocean who surfaces in search of a rare, savory type of worm.
- Ascended Meme: Was originally supposed to be the boss of an April Fools' Day joke, the Tidal Moon event. While the event isn't real, Duke Fishron is.
- Berserk Button: If you lure him out of the Ocean biome, he will become more aggressive and damaging.
- Bubble Gun: Spits homing bubbles at the player.
- Bullfight Boss: While he does have other attacks, Duke Fishron's primary form of offense is charging at the player repeatedly. In his Expert Mode third phase, he will only attack by charging.
- By the Lights of Their Eyes: His Expert Mode ability shrouds the entire area in fog while he turns invisible, and his glowing eyes is one way to detect him before he charges.
- Desperation Attack: He gains one when he's at very low health on Expert Mode. It involves him turning the screen dark while he turns invisible before he charges you.
- Flunky Boss: Summons Sharknadoes and Cthulhunadoes that spew out flying shark projectiles called Sharkrons.
- Flying Seafood Special: He's a huge flying fish.
- Glowing Eyes of Doom: When he Turns Red.
- Homing Projectile: His bubbles and his Cthulhunado typhoon.
- Immune to Flinching: Duke Fishron is one of the very few bosses in the game that cannot be stunned nor slowed by the Heart Arrows, which can otherwise stun even the Destroyer, Wall of Flesh and the Dungeon Guardian!
- Implacable Man: Got buffed in 1.3—he will repeatedly charge at you if you exit the ocean, instead of charging five times then attacking.
- The Juggernaut: It will only stop when it's transforming to its second state, pumping out bubbles or dead. He's also immune to the Stunned debuff.
- King Mook: To both a Mook (Pigron) as well as a particular fishing catch (Fishron).
- Lightning Bruiser: Extremely fast, extremely painful, and sports at least 50,000 health, more than most of the other bosses.
- Mix-and-Match Critters: A fish-pig-dragon mutant creature.
- Mutant: The official achievement unlocked by beating him outright calls him one.
- Nintendo Hard: Deals painful damage with his attacks, moves extremely fast, and a lot of health to wear down. Speed-increasing items and Wings are pretty much mandatory if you don't want to be torn to shreds. In 1.3 and above, you're also constrained to fighting him within the ocean, or else he gets pissed.
- Number of the Beast: The Truffle Worm used to summon him has a 666% Fishing Power. In addition, the Fishron Wings you can get for beating him have a 6.66% drop rate.
- Ramming Always Works: Has a high tendency to ram the player.
- Shout-Out: Has the ability to summon Sharknadoes.
- Superboss: Like the Empress of Light, he doesn't need to be beaten in order to fight the Moon Lord, and you need to go somewhat out of your way in order to summon him. He's also much tougher than most of the other Hardmode bosses despite being able to be potentially summoned before any of them, but his drops will make the rest of the game a lot easier.
- Teleport Spam: In his third phase in Expert Mode, Duke Fishron will frequently teleport around the player before charging.
- Trademark Favorite Food: He can only be summoned via a Truffle Worm.
- Turns Red: Gains Glowing Eyes of Doom, charges faster but less often, and changes his bubble spray into a spinning spray that creates more bubbles and his Sharknado into a Cthulhunado which is much larger, homes in on the player before deploying, and summons many more Sharkrons. The Fishron Mount obtained from him in Expert Mode allows the player to do this—when low on health, the player gains an attack and speed buff.
- Expert added a third phase to his fight: at critical health, he will darken the screen, turn invisible, and continuously charge at you while constantly teleporting to approach you from different angles.
- Victor Gains Loser's Powers: When the player beats him, they get equipment based on his abilities: Flairon and Bubble Gun are based on his bubble spray, Tsunami is based off his relentless charges, Razorblade Typhoon is based off his Cthulhunado-spawning homing typhoons, the Tempest Staff is a smaller Sharknado, Fishron's Wings give the player the Duke's superior air and water mobility, and the Expert Mode Shrimpy Truffle nets the Duke himself as a mount, allowing you to Turn Red when low on health.
Lunatic Cultist
"The fanatical leader of the Dungeon coven..."
- A fanatical leader hell-bent on bringing about the apocalypse by reviving the great Cthulhu through behind-the-scenes scheming.
- Ambiguously Human: Human in appearance, yet his body is completely covered with even his face being masked. He possesses insanely powerful inhuman abilities and his Voice of the Legion implies that he's something entirely different.
- Apocalypse Cult: He's the leader of them.
- Beef Gate: In order to prove that you have a chance to deal with the Pillars and their wide range of coverage, you have to kill him first. Especially since there's no way to get rid of the Pillars once summoned aside from destroying them.
- Big Bad: In the 8th Anniversary Lore, he's the one behind several of the events, including the Old Man and the Dungeon being cursed as well as being responsible for the Mechanical Bosses by having the Mechanic kidnapped and forced to assemble them. Finally, he's the one who summons the Celestial Towers, and by extension the Moon Lord.
- Big "NO!": He says this upon death.
- Doppelgänger Attack: If you fail to interrupt his Doppelgänger Spin, the copies follow him around in an upside-down 'V' formation and are able to attack you. They can't be damaged or destroyed until his next spin, which will cancel them out if you do it right.
- Doppelgänger Spin: After several magic attacks, he'll create several copies of himself surrounding a runic circle. If you don't hit the original (distinguished by a yellow vertical stripe on his hood, among other minor differences), it becomes a Doppelgänger Attack and he summons a phantasm dragon. Each time you fail this, he gains more copies until you get it right.
- The Dragon: He's the one in charge of the Lunatic Cult and is therefore the greatest servant to the being he worships, the Moon Lord, also being responsible for the summoning of said Moon Lord.
- Dragon-in-Chief: On account of the Moon Lord being sealed away, he is the one actively responsible for many of the game’s events.
- Duel Boss: Fights you mano-a-mano without the aid of any allies beyond what he can create if you don't interrupt his summoning spell.
- Evil Sorceror: Very much so.
- Evil Sounds Deep: His voice sounds inhumanly deep as he prays to the stone in Black Speech before absorbing it and turning his attention to you.
- Fire, Ice, Lightning: Can cast homing fireballs, ice crystals that fire ice spikes, and lightning bolts.
- "Get Back Here!" Boss: He teleports all over the place between attacks and always tries to stay above you, even if you try to chase him down using flight.
- Humanoid Abomination: The Lunatic Cultist may look human, but his exceptional magical strength as well as his voice, which borders on Voice of the Legion, heavily implies that he may have traded his humanity to become something not of this world.
- Instant Runes: He will create a massive runic circle just before creating a doppelgänger and attacking.
- Lightning Bruiser: Don’t let his Squishy Wizard tendencies fool you. He’s fast enough on his feet to Flash Step, can summon powerful spells and monsters very quickly and can take a beating that would tear lesser foes to pieces many times over before finally expiring.
- Magic Missile Storm: Once he takes enough damage, he starts to cast Ancient Light, firing two spreads of painful homing projectiles at you. Thankfully, said projectiles are destructible.
- Meaningful Name: He's lunatic in both senses of the word—crazy, and also moon-related.
- Playing with Fire: One of his attacks is to hurl homing fireballs at you that explode on impact. In certain circumstances he can combine this with Casting a Shadow and start tossing shadowflame fireballs as well.
- Plague Doctor: He's got the outfit of one, at least. You can get said plague doctor mask as a drop, and it's also the trophy you obtain from him.
- Puzzle Boss: Part of his boss fight involves a Spot the Imposter phase where hitting the wrong Lunatic Cultist will let him summon additional minions—a Phantasm Dragon and Ancient Vision.
- Spread Shot: His Ancient Light attack fires two spreads of homing magic projectiles which hurt a lot, but are thankfully destructible.
- Shock and Awe: One of his attacks is to summon a giant ball of energy that hurls lightning bolts at the player.
- Squishy Wizard: He has extremely low HP when compared to most of the other hardmode bosses, but he can deal out damage very quickly with his wide variety of magic attacks. He mitigates his frailty somewhat by moving around constantly and being hard to hit.
- Turns Red: He gains a new attack in the form of Ancient Light when he reaches around half his health.
- Unstable Equilibrium: The fight with him can either be reasonably difficult or downright impossible, depending on your ability to interrupt his Doppelgänger Spin.
- Xanatos Gambit: Seems to absorb the sealing magic of the Mysterious Tablet in order to gain power AND ensure a victory on some level. Either you kill him and break the seal of the Celestial Pillars, or he kills you and can continue his plans unhindered.
The Celestial Towers (Vortex, Nebula, Solar, and Stardust Pillar)
"Celestial creatures are invading!"note
- Representing a deep celestial void/stormy celestial body/flaming celestial event/glittering celestial remnant known as "vortex/nebula/solar flares/stardust", this tower holds the seal locking away the terrifying tyrant.
- Amazing Technicolor Battlefield: All of them turn the background to an ominous moon with coloured background when fought. Each of their fragments can be used to craft a Monolith that can display their respective backgrounds at will.
- Anti-Air: Go too high off the ground near the Solar Pillar, and you will be attacked by a Crawltipede; as they're massive, heavily damaging, and only take damage if you attack their tail segments, it's generally not something you want to happen. Fortunately, Crawltipedes can only attack airborne players; if you're standing on something solid, they'll leave you alone.
- Asteroids Monster:
- The Stardust Pillar's Star Cells will split into multiple small Cells when killed. If left unattended, these small Cells will grow into full-sized Star Cells and start the process over again.
- Alien Queens from the Vortex Pillar will release Larvae upon death that can grow into Alien Hornets, which in turn will become more Alien Queens if not dealt with.
- Attack Reflector: Selenians, summoned by the Solar Pillar, can attack with a spinning dive that also reflects incoming projectiles.
- Brown Note: It's suggested by the messages that appear after destroying them that they have a pretty bad effect on the player character. It is not clear whether this is the Towers' doing or the Moon Lord's.First Tower: "Your mind goes numb.."
Second Tower: "You are overwhelmed with pain..."
Third Tower: "Otherworldly voices linger around you..." - Cosmic Entity: They have the markings of this as they both draw power from and seem to embody on a level their respective cosmic forces in the universe.
- Deflector Shields: When first encountered, they have a clear forcefield around them that makes them invulnerable. It's only when you kill off 100 (150 in Expert) of their minions that the shield breaks.
- Eldritch Abomination: All four of the pillars are some kind of otherworldly aliens. It's unknown if they're even sentient. Many of the Mooks they teleport in also fit this, if they aren’t humanoid or resembling various terrestrial animals.
- Energy Weapon: The preferred attack method of the Nebula Pillar's Nebula Floaters and the Vortex Pillar's Alien Queens and Storm Divers. Their lasers are among the more damaging attacks in the Lunar Events.
- Fighter, Mage, Thief: And Summoner. Each of the towers are based on a method of offense — Solar for Fighter, Nebula for Mage, Vortex for Ranger, and Stardust for Summoner. The Lunar Fragments they drop are also used to craft equipment corresponding to the respective tower's type.
- Flunky Boss: The pillars do attack, but mainly rely on spawning minions. It's also required that you beat enough minions first in order to attack the boss itself. Once their shields are down, though, they are practically helpless and only have 20000 HP.
- Hero Antagonist: Their appearance is a last ditch effort to stop the Moon Lord from being released.
- Humanoid Aliens: Each pillar summons at least one humanoid enemy: Stargazers for the Stardust Pillar, Predictors for the Nebula Pillar, Drakanians and Selenians for the Solar Pillar, and Vortexians and Storm Divers for the Vortex Pillar.
- Increasingly Lethal Enemy: Alien Larvae around the Vortex Pillar are nearly harmless. Then they grow into manageable Alien Hornets, which will grow into deadly Alien Queens that drop more Larvae on death.
- Last Ditch Move:
- Vortexians will summon a portal that releases a lightning bolt at the player when killed.
- Flow Invaders attack by generating minions that they shoot as projectiles, one at a time. When killed, the Flow Invader will launch all of its remaining minions at once.
- Mook Maker: Besides the bosses themselves, the Stardust Pillar's Twinkle Poppers will summon Twinkles, small minions that explode on contact.
- Our Wormholes Are Different/Swirly Energy Thingy: The Vortex Pillar creates these around the player, which spawn Alien Hornets.
- Playing with Fire/The Power of the Sun: The Solar Pillar's mooks are rather fiery and sun-like, and the pillar itself will attack with a shower of fireballs, many of which can be seen raining down in its background.
- Shock and Awe: The portals created by the Vortex Pillar can sometimes shoot a bolt of lightning at you, instead of spawning more Mooks.
- Shotguns Are Just Better: Storm Divers wield laser shotguns. It's certainly not better for the player, though, as they deal quite a bit of damage if the Storm Diver can line up a shot.
- Shows Damage: Every time one of their minions (besides Crawltipedes) die, they generate a bolt of energy that strikes the Tower's shield and causes it to visibly weaken. The shield itself gets more and more transparent until finally bursting.
- Starfish Aliens: Most of the minions summoned by these things are pretty weird looking. The Pillars themselves may also count.
- Star Power: Of the Lovecraftian sort. The Stardust Pillar is able to create "stars" around it that spawn Star Cells and Milkyway Weavers.
- Stationary Boss: They don't move at all, and none of them apart from the Solar Pillar are directly capable of attacking you.
- Teleport Spam: Nebula Floaters teleport around frequently while firing lasers in your general direction.
- Well-Intentioned Extremist: The Pillars are physical anchors meant to keep the Moon Lord imprisoned, and it can be assumed that the invaders are actually defending them to prevent you from breaking the seal.
Moon Lord (Cthulhu)
- The mastermind behind all terrors which befall the world, freed from his lunar prison. Practically a god, his power knows no limits.
- All Your Powers Combined: He carries many notable traits from bosses that were torn from his body, with Skeletron's general structure of "two hands and a head", the true Eyes of Cthulhu charging around like the original, and the Brain of Cthulhu's orbiting eyes.
- Ancient Evil: The 8th Anniversary Lore states that he arrived to Terraria long ago to rain destruction and to dominate all sentient life, but was heavily wounded and driven away to the moon by the Dryads. The Lunatic Cultist plans to bring him back in the current day.
- Anti-Regeneration: When he's leeching energy from you, he applies the Moon Bite debuff which makes that affected player's lifesteal effects useless.
- Attack Its Weak Point: The giant beating heart in his chest. The problem is that you must destroy all three of his eyes if you want him to expose it.
- Background Boss: Stays in the background all the time. However, touching its eyes (or where they used to be) will deal Collision Damage.
- Battle Theme Music: One of six bosses with their own theme music, in his case an appropriately eldritch tune simply titled "Moon Lord".
- Beam Spam: The Moon Lord excels at this, with his entire offensive pattern being pretty much trying to obliterate the player with endless volleys of eldritch-plasma blasts while trying to pick them off with up to three giant laser blasts in one go.
- Body Horror: His body from the neck down looks mostly human, but everything below the chest is missing, complete with exposed ribs and spine. His Cthulhu head also has an exposed brain, his heart is exposed through his chest, and his forehead and hands both have eyes set into them that can pop out and leave a gaping maw behind.
- Boss Vulnerability: Each of the targetable eyes are a Wait Them Out sort, while the heart is Always Vulnerable once it's exposed.
- Came Back Wrong: The Lunatic Cultist's ritual was supposed to bring him back to life in full power, but the player interrupted it, forcing Cthulhu back to life in an incomplete state, lacking anything below his ribcage and having an exposed brain. It's explicitly stated that he's weaker as the Moon Lord than he was before his death.
- Cognizant Limbs: The eyeballs in his hands and his Third Eye can attack separately and must be destroyed for him to expose his core.
- Damage-Sponge Boss: His component parts have collectively more health than anything in the game. His Third Eye and heart have more health than every other boss save the Destroyer.
- Darkness Equals Death: He turns the background around him black, so if you lose track of him, a good way to find out where he's gone is the background rapidly growing darker as he slowly comes back. He’ll also turn campfire flames black when he’s summoned.
- Eldritch Abomination: An eldritch horror from the depths of space.
- Evil Is Bigger: The largest enemy in the game as of 1.4 and the Final Boss.
- Extra Eyes: He has five eyes on his head (although only one is targetable) and one on each palm.
- Expy: Heavily resembles Cthulhu. His eyeball minions are even called "True Eye Of Cthulhu". 8th Anniversary Lore Event drops the Expy part entirely though, referring to him simply as Cthulhu instead of as the Moon Lord.
- Expy Coexistence: The creators joked that he was Cthulhu's brother.
- Eye Beams: His forehead eye can fire out a powerful Phantasmal Deathray while the eyes on his palms can fire laser shots. When his eyes are detached and become True Eyes of Cthulhu, they can use a weaker version of the Phantasmal Deathray.
- Eyes Are Unbreakable: Depleting the health of his eyes will simply cause them to pop out and become invulnerable True Eyes of Cthulhu instead of destroying them.
- Eyes Do Not Belong There: Has an eye in each of his hands. He can also fire countless energy eyeballs at you for his attacks.
- Final Boss: Is this for the entire game. Getting him to appear requires defeating almost every other boss. He is fittingly the absolute last thing on the Bestiary.
- Flunky Boss: When each eye is beaten, they will become an invincible flunky that attacks on its own.
- Go for the Eye: The Moon Lord's eyes are his weak points in his first phase.
- Greater-Scope Villain: The 8th Anniversary Lore has him as the main antagonist that threatened Terraria long ago and his missing body parts are early game bosses but he has long since been sealed away and only appears for one boss fight. The Lunatic Cultist is the one who not only causes far more immediate problems (namely the creation of the mechanical bosses) but is the one who allows him to break free from his seal in the first place.
- Handicapped Badass: Is clearly still reeling from his defeat long ago evident by his entire missing lower half, but will give the player the fight of their life.
- Homing Projectile: Can fire Phantasmal Eyes that home in on players and explode.
- Implacable Man: Do not let his slow movement fool you, this guy will never stop coming unless he kills you or dies trying. He will never despawn unless you die, so he'll chase you quite literally to the ends of the earth and the fact that he teleports to you when you get far enough away from him doesn't help.
- Informed Flaw: The 8th Anniversary Lore states that the mechanical bosses were meant to be used in rebuilding and replacing the body parts he lost, but he's completely lacking in cybernetics, has two arms as opposed to Skeletron Prime's four and glowing teal eyes rather than the red and green-irised Twins, though the player destroying those prosthetics and then interrupting his resurrection ritual may have something to do with this. Not justified by their chaos is the fact that he does have a cyan brain; the Brain of Cthulhu is pink and was never turned into a mechanical boss before the player freed the Mechanic.
- Kaizo Trap: Before the Journey's End update, the holes where his weak points used to be will still hurt you during his death animation; if you're low enough on health, you'll get killed and he'll disappear without leaving behind any of his valuable drops or giving you the achievement for killing him.
- Life Drain: Has an ability where his mouth sends out a sucker that starts draining balls of energy from you. If the balls are not destroyed before they reach his mouth, he regenerates health. During this, he'll inflict the Moon Bite debuff which also prevents you from lifestealing from him for the next fifteen seconds or so.
- Lovecraft Lite: The 8th Anniversary Lore downplays this as the Dryads were all but wiped out barring one during the battle, but they did kill and seal him away. Ingame it's played straight as the player can kill him without much trouble using mostly equipment from the planet itself.
- Mighty Glacier: The most powerful boss, and yet also one of the slowest. Granted, that's only his movement speed, his rate of attack is a different story entirely.
- Monster Progenitor: Most of the pre-Hardmode bosses are implied by lore to be parts of his body that were torn off in his battle against the Dryads.
- Mutual Kill: Was torn to pieces by the Dryads and forced to retreat, leaving only his scattered body parts behind, but annihilated the Dryad civilization and killed all but one of them in the process.
- No-Sell:
- He's immune to lifestealing effects from the Spectre Armor and the Vampire Knives when he's leeching energy from you.
- As of 1.3.0.6, it's impossible to "cheese" him via using Mercy Invincibility from other sources of damage—he will still hit you.
- Nothing Is Scarier: Before he appears, the background music ominously disappears.
- Organ Autonomy: Even his detached organs are essentially Eldritch Abominations in their own right.
- Power Floats: Floats around the area effortlessly.
- Red Baron: When the status message says "Impending Doom approaches", it doesn't just mean a sense of it; The Moon Lord bears a literal title of "The Impending Doom".
- Retcon: Initially, Cenx stated that the Moon Lord was the brother of Cthulhu. This was later revealed to be a joke. Red eventually clarified by adding that the Moon Lord is Cthulhu, albeit nowhere near full power and lacking a complete form.
- Rasputinian Death: His ability to endure mortal injury and keep on going is downright absurd. In the lore the Dryads really did a number on him, with the Moon Lord having been literally bisected, disembowelled and losing his eye along with at least some of his brain and bones before being finally sealed away. When he’s unsealed and does battle with the player, three more of his eyes are gouged out over the course of the lengthy fight and it takes the player pulverising his exposed heart with all they have for him to kick the bucket, with the resulting death knell vaporising all the remaining flesh on his body and reducing him to a skeleton.
- Sequential Boss: His three main eyes must be destroyed first, then his core will open.
- Serial Escalation: First came the Eye of Cthulhu, an eye that attacks you on its own. Then came the Twins, two eyes who attack you in tandem. Then the Moon Lord one-ups them both, spawning three True Eyes of Cthulhu as you whittle down his health.
- Sickly Green Glow: Various parts of his body glow blue-green, and while he's alive, the entire screen will be tinted the same color.
- Status Infliction Attack: Moon Bite is of the Decover type, preventing Life Drain effects from working on him.
- Stripped to the Bone: When beaten, his skeleton drops to the ground.
- Super-Persistent Predator: Will chase the players across the map. 1.3.0.4 made it such that he just teleports right to you if you get too far from him.
- Tactical Suicide Boss: The Moon Lord's forehead eye is closed and cannot be attacked most of the time. It only opens to fire the Phantasmal Deathray, at which point it becomes vulnerable to damage.
- Third Eye: While he has four other eyes on his head (and one on each hand), the one on his forehead is the most prominent: it has the most health, is closed for most of the time and is the only one that can fire the Phantasmal Deathray.
- Tom the Dark Lord: When saying he was Cthulhu's brother, the creators joked that his name was Steve.
- Wave-Motion Gun: Can fire a Phantasmal Deathray from his Third Eye. It sweeps around from one side of the screen to the other and does a great amount of damage while penetrating solid blocks. When an eye is detached, it can use a similar but weaker laser.
- Who Needs Their Whole Body?: Is capable of being an apocalyptic threat even after having been bisected, disemboweled, de-boned, blinded, and lobotomized. In fact, the parts that were taken out of him just got up and started their own reigns of terror.
- Worf Had the Flu: It's implied that he was not at full power when battling the player, as his physical form was incomplete.
- You Will Not Evade Me: The 1.3.0.4 update made it such that he teleports right to you if you get too far from him.
