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Sword Art Online

General

Confusion Fu: To a degree. As evidenced by Illfang, there have been changes made to the bosses from how they were in the Beta, which can render knowledge from Beta-Testers, who are the best sources of knowledge in SAO, inaccurate and potentially even useless in some instances.
Generic Doomsday Villain: As NPC monsters with low level AI, they lack true sentience to be deemed evil. But that doesn't stop them from being the main threats of the Aincrad arc.
The Heavy: While Kayaba is the Big Bad, these guys are the main threats the Clearers have to deal with, being the things standing in their way and preventing them from reaching higher floors.
King Mook: A lot of the Floor Bosses are effectively larger versions of, and in some cases The Leaders of the Mobs that plague the Floor they're the Boss for,
- Aside from your basic wolves and boars, the main threat of Floor 1 appear to be Kobolds. The Boss of the floor is Illfang the Kobold Lord, who has a few of them as bodyguards.
- Floor 2 is comprised largely of mobs resembling cows or bulls, the most dangerous among them being minotaur's wielding hammers who can inflict stun with a shockwave attack. Fittingly, the bosses of the floor consists the highest ranking members of these monsters, Colonel Nato, General Baran and King Asterius.
- Floor 5 consists of giant golem enemies and Astral-type enemies. Not only is the Floor Boss a magical golem made by a king wishing to wipe out a dwarvern kingdom, but the king in question appears as an undead sub-boss.
- While Floor 10 has yet to be seen, Kirito mentions that one of the monster types there are "Snake Samurai". In Ordinal Scale, it's revealed that the boss for Floor 10 was Kagachi the Samurai Lord, a giant reptilian creature clad in Samurai armor and wielding a massive Katana.
Orcus on His Throne: In some cases, the Floor Bosses are either the leader of certain monster types, like Illfang with the Kobolds, or the Big Bad of a questline on the floor. However, they're never fought until the Boss Room is discovered and they are engaged.

Floor Bosses

Floor 1 - Illfang the Kobold Lord

Illfang the Kobold Lord

The leader of the Kobolds plaguing Floor 1, as well as the game's first boss.

Adaptational Curves: In his redesign for the Progressive: Aria of a Starless Night Motion Picture, virtually all of Illfang's body-fat is replaced by slabs of muscles plastered on a towering, long-limbed 15-foot-tall frame, turning him him from a formidable but ridiculous-looking foe into a hulking, terrifying beast that stomped out of your darkest nightmares.
And Your Reward Is Clothes: He drops the Coat of Midnight, which Kirito takes to wearing after his Zero-Approval Gambit.
Adaptational Dye-Job: In the original Light Novel, he has grey skin. In the anime and subsequent adaptations, his skin is instead a deep red color.
Acrofatic: For a giant, Fat Bastard of a monster, he has no issue leaping large distances and wall-jumping off the pillars in his throne room. Though all his body-fat are replaced by bulging muscles in Aria of A Starless Night, he is correspondingly more agile and even faster.
Brutish Character, Brutish Weapon: In the first phase of his fight, he wields a axe in conjunction with a buckler shield. On his last health bar, he'll toss both away in favour of a nodachi.
Death from Above: Its most powerful attack is to jump high up in the air and bring its axe down.
Every Japanese Sword is a Katana: His back-up weapon is referred to by everyone as a Nodachi, but his large size means that he can use as if it's a regular Katana, allowing him access to Katana Sword Skills.
Fat Bastard: A large, port-bellied beast, and leader of a group of monsters. Completely averted however with his tall and muscular terrifying redesign for the Progressive: Aria of a Starless Night Motion Picture.
Flunky Boss: He fights accompanied by a group of Ruin Kobold Sentinels, who are tasked with defending him. He is assisted by twelve in total, starting with three and another three spawning for every time he loses a health bar.
Hero Killer: Due to a change from the Beta, he's able to catch Diaval off-guard and kill him.
Katanas Are Just Better: He goes from using a Talwar in the Beta to using a Nodachi at his last health bar in the main game, a change that catches the raid party off-guard and leads to Diavel’s death.
Klingon Promotion: The in-game lore reason for his change in weapons is presented as this in the Progressive Manga. A mural Argo discovered after he's defeated depicts two large, port-belied Kobolds; one using a Nodachi and standing victorious, and the other using a Tawlar and laying defeated on the ground.
Large and in Charge: Fitting his status as their Lord, Illfang is a lot larger than your run of the mill Kobold, being more muscular and larger.
Luckily, My Shield Will Protect Me: In his first phase, he'll use a buckler shield in conjunction with his axe.
Our Kobolds Are Different: He also looks more like a giant obese kangaroo than traditional kobolds.
- In Aria of a Starless Night, however, he is closer to the actual red-kangaroo that inspired his design, a tall hulking brute bulging with muscles.
Recurring Boss: In the Rising Steel Event "Aincrad Side Stories: Secret Battle", the Boss for the Floor the frontlines are on is revealed to resemble Illfang and functions similarly to him, starting with an axe and shield before switching to another weapon on his last health bar. Unlike Illfang however, Light the Kobold Lord instead switches to using Martial Arts as opposed to a Nodachi, with a short sword to throw at players.
Turns Red: When he's at his last Health Bar, he throws away his axe and buckler in exchange for a large Nodachi, which allows him to use Katana Sword Skills and he proves to be extremely quick and Acrofatic while wielding it.
Unwitting Instigator of Doom: By killing Diavel, he inadvertently kickstarts the Beta-Tester Witch Hunt and prompts Kirito's Zero-Approval Gambit. It also causes the Frontlines to end up in the dysfunctional state it's in now.

Floor 2 - Tauruses

The Tauruses

The collective bosses of Floor 2, a duo, now trio of giant Minotaurs, one larger than the next.

Moveset Clone: The three of them are effectively similar, with the differences being their sizes, damage output and health. The most different of them is Asterius, who has his own unique version of Baran and Nato's Signature Move and possesses an Electric Breath Weapon.
Status Infliction Attack: A large part of their strategy is trying to afflict Players with Stun then Paralysis. Their main method of doing this is by using Numbing Impact/Detonation to stun players, then using it again to inflict the Stunned players with Paralysis.
Turn Red: All three of them do this when they're at their last health bar, at which point they will spam Numbing Impact and Asterius' Numbing Detonation as often as possible.

Nato the Colonel Taurus

The original Mid-Boss to General Baran, until the main game where he shared the role with Baran as Mid-Bosses for Asterius.

Curb-Stomp Battle: After Asterius appears, Kirito and the Legend Braves make quick work of Nato to lower the enemy numbers. They're able to do this easily thanks to his HP being low.

Baran the General Taurus

The original main Boss of Floor 2, until the main game where he becomes a sub-boss for Asterius.

And Your Reward Is Clothes: As a Last-Attack Bonus, he drops a pair of Gold Bull-Pattern Boxes, a pair of red underwear with a bull symbol on the back that grants a buff to strength and a minor resistance to status ailments such as disease and curses.
Degraded Boss: From the main boss in the Beta to a Sub-Boss to King Asterius in the final release.

Asterius The Taurus King:

A new third boss of Floor 2, who appears partway through the fight with Baran and Nato.

Adaptational Wimp: Zig-Zagged. In the Manga version, he lacks a hammer and is instead reliant on his breath attack and his bare hands. However, this isn't presented make him any less of a threat.
Attack Its Weakpoint: His weakpoint is the crown on it's head, which will cause him to stagger when hit. However, due to his height, it can only be hit by ranged weapons, such as a Chakram.
Attack of the 50-Foot Whatever: His size is phenomenal
Breath Weapon: He possesses a Lightning Breath attack that has a high chance of stunning or paralyzing it's targets, and is capable of travelling it's full range in an instant. The Tell for when this activates is his eyes glowing.
Dark Is Evil: He's described as having black, ink-like skin.
EX Special Attack: Instead of the "Numbing Impact" used by Baran and Nato, he uses the more dangerous "Numbing Detonation", which possesses twice the range of the "Numbing Impact".
Flunky Boss: His flunkies just so happen to be his top military commanders.
Giant Space Flea Out Of Nowhere: Subverted. While to the Raid Party he could appear to be this, since they had no warnings of his presence, he actually gets some Foreshadowing in the form of a quest Argo undertook, which leads to a mural depicting him with Baran and Nato.
The Tell: Has two to warn players when he's using his Signature Moves.
- When he's using his Lightning Breath, his eyes will glow.
- When using his "Numbing Detonation", he'll stomp his hoof three times and raise his hammer.

Floor 3 - Nerius The Evil Treant

Nerius The Evil Treant

A sentient tree monster that uses poison attacks.

Breather Boss: In-Universe. Unlike Illfang and the Tauruses, he's hinted to have been comparatively easier due to the Raid Group's supply of antidotes making it's poison attacks null and Asuna's Chivalric Rapier allowing her to deal massive damage to it.
Killed Offscreen: His battle is largely glossed over, the only things of note being that he was easy thanks to Asuna's rapier and a steady supply of antidotes, and that Morte didn't take part in the fight against it.
Poisonous Person: It uses wide AoE poison attacks that it lacked in the Beta, but it didn't prove to be effective due to the Raid Party bringing a large supply of antidotes.
When Trees Attack: It's a giant, poisonous tree.

Floor 4 - Wythege the Hippocampus

Wythege the Hippocampus

A horse-fish with the ability to cause water to emerge even from dry land.

Combat Tentacles: It has a full mane of these.
Curb-Stomp Battle: The fight against Wythege started as one in his favor, with Kirito and Asuna's absence and it's water ability giving it a great advantage, even if he didn't kill anyone by the time Kirito and Asuna arrived. However, when Yofillis joined the fray with his ring that lets him walk on water and the players figured out how to decrease the water level, Wythege quickly ended up on the receiving end.
Killed Offscreen: Like Nerius, his defeat is largely glossed over. Averted in the Scherzo movie as his defeat is shown in the opening scene.
Making a Splash: It's special ability, Water Inflow, allows it to submerge the boss room in water. The only counter for this is to open the door to the boss room, which can only be done from outside.
Our Hippocamps Are Different: He's a cross between a horse and a fish.

Floor 5 - Fuscus the Vacant Colossus

Fuscus the Vacant Colossus

A giant colossus created by a human king wishing to wipe out a rivalling drawfvern kingdom but became inactive when Aincrad was created. Due to it holding a Flag of Valor, an item that boost the stats of guildmates, Kirito is forced to form a party to defeat it when Morte informs the ALS, putting the Frontline's power-balance at risk.

Attack Its Weak Point: Initially believed to be the forehead, it's true weak-point is revealed to be the glowing symbol on it, which Fuscus can move between limbs to prevent it from getting hit.
Attack of the 50-Foot Whatever: It's not called a "Colossus" for nothing. In its Final Form, it's even bigger than Asterius the Taurus King, whose head nearly touched the ceiling of his Boss Room.
Boss Room: He is the Boss Room. In the first phases of his fight, his body, head, arms and legs are merged with the walls, ceiling and floor. This allows him to pop out of anywhere to attack players, such as the staircase out of the room, which Shivata learns the hard way when he nearly gets eaten by him. He'll drop this and come out himself once his HP is low enough.
Golem: He's a giant made from magical ore, made by the ruler of a human kingdom who wished to wipe out a nearby dwarwvern kingdom, as they were trade rivals with his kingdom. However, The Great Separation and removal of magic that created Aincrad occurred, leaving it inactive.
Clothing Damage: His grab move has the added benefit of lowering the durability of armor, making it especially devastating to heavily armored tank players if they're caught by it's ambush.
Damage-Increasing Debuff: Once the head appears, it'll let out a roar that applies a defense debuff on the entire raid party. It retains this during it's final phase.
Grapple Move: It's opening move is to grab players who step on the blue lines on the Boss Room Floor and attempt to crush them to death, damaging their equipment in the process. The only way to break his hold is using a Sword Skill at a certain level or power.
The Heavy: He drives most of the conflict in Floor 5, as his possession of the Flag of Valor, an item that grants a stat boost to all players in the same guild as the wielder, as a drop prompts the ALS, after being informed of it by Morte and pressuring Kibaou into giving the go-ahead, to try and take it from under the DKB's noses, putting the power balance between the two Guilds at risk. This forces Kirito to bring together a Ragtag Bunch of Misfits to beat it before the ALS can and preventing the other Guild from collapsing in the process.
I'm a Humanitarian: Attempts to eat Shivata when the party tries escaping the Boss Room. Thankfully, he's rescued with the help of Liten, who pries the mouth open, and Kirito, who realizes that he moved his weapoint to his arm or legs and leads Asuna, Argo and Nezha in finding it.
Knight of Cerebus: Unlike the previous two bosses who are largely glossed over, Fuscus is treated much more seriously due to how much of threat the Guild Flag it drops is to the current nature of the Frontlines and due to being legitimate threat, unlike the last two who had easily exploitable flaws and weaknesses.
Meaningful Name: His title of "Vacant Colossus" refers to how he's also the Boss Room itself; he's effectively an empty room who can launch his limbs from the floor and ceiling to attack players.
Puzzle Boss: Starts off as one. When the fight begins, he is nowhere to be seen but what are around are a bunch of glowing blue lines on the floor. Stepping on them will cause him to try grabbing or stomping on the players, which are the only openings in which players can attack it.
Red Eyes, Take Warning: At it's final phase, the circular rings shapes representing it's eyes will turn red, along with the rest of the lines on its body.
Stuff Blowing Up: When he's finally defeated, the red lights on it's glow brighter and brighter before emitting flames and finally exploding, something Kirito notes is much more of a spectacle than the previous boss deaths.
Turn Red: Once he's at his final HP Bar, Fuscus will leave the confines of the Boss Room's walls and form into a more traditional Golem. In this state, he makes use of punch and stomp attacks, as well as it's above-mentioned Damage-Increasing Debuff and Eye Beams.

Floor 6 - The Irrational Cube

The Irrational Cube

A giant Rubix-cube-like creature with a Sudoku puzzle on each of it's sides. According to the Stachion questline, it's actually the source of the Curse of the town that makes almost every door locked by puzzles.

Adaptational Name Change: In-Universe. In the Beta-Test, it was called “The Irritating Cube”. In the official release, it was renamed "The Irrational Cube".
Adapted Out: It does not appear in Integral Factor, with the Floor 6 boss getting replaced with "Pierce the Rogue Manticore". Likely owing to how difficult it would be to add the puzzle solving mechanic into the gameplay.
Artifact of Power: The Irrational Cube, or the more accurately the Golden Cube used to power it, is actually a magical tool capable of deconstructing, "Break", and reconstructing, "Bind" structures, and is what Pithagrus used to build Stachion. It's also capable of inducing a special paralysis effect on players with the "Bind" commanded, which Buxum uses once he gets the chance to try and kill Theano and possibly the entire Raid Party.
Beam Spam: It's main method of attack is firing laser beams from its corners at players.
Bright Is Not Good: Shines a brilliant, gold color while being fought.
Draw Aggro: It seems to automatically target anyone who hits it and rotates it's cubes, something an ALS member by the name of Schhinkenspec learns the hard way when it uses a Sword Skill on it. This goes even further when it targets Asuna when she starts instructing players on how to solve its puzzles.
Marathon Boss: In the end, it ends up taking over an hour to defeat. And the hour in question is spent trying to escape the Boss Room.
Mighty Glacier: So long as its puzzle is unsolved, the Irrational Cube is effectively invincible and the lasers it fires can deal quite a bit of damage. Thankfully, it's lasers are easy enough to dodge if you remain focused or aren't too close to it when it fires at you.
Puzzle Boss: As the name and design implies, the Irrational Cube is this. In the beta, where it was called the Irritating Cube, it operated just like a Rubix Cube in that all sides needed to have only one color before it could be damaged. In the final game, where it's called “The Irrational Cube”, each side instead has a Sudoku puzzle on each side operates like a rubix cube, meaning you need to solve the puzzle on each side and turn the parts to make all the numbers match, making it a lot more complicated.
- This even applies to leaving the Boss Room, with the door, at least on the inside, being locked by a series of Sudoku puzzles.
Sequential Boss: It has three phases:
- The first, and arguably the longest phase, is spent on actually solving the Puzzle, which is basically the demonic love child of a robix cube and sudoku, only with Energy Weapons.
- In the second phase, the puzzle being solved causes it to lose all it's armor and it grows extra arms to compensate, turning it from a Mighty Glacier into a Glass Cannon, with it's attacks being roughly the same but, with the combined efforts of the Raid Party, Theano and Myia, it ends very quickly.
- The final phase is honestly hardly even as a phase. The cube just loses all it's armor and falls to the floor, waiting to be hit and destroyed. The only reason the fight doesn't end then and there is because Buxum of the DKB reveals himself as The Mole and uses the Golden Cube to freeze everyone.
Turn Red: It appears to grow progressively more aggressive the closer the puzzles on it get to completion, even growing arms made of cubes that it can swing at players.

Floor 7 - Aghyellr the Igneous Wyrm

Aghyellr the Igneous Wyrm

A giant warm that can breath powerful flames.

An Arm and a Leg: When Nirrnir attempts to use the Sword of Voluptia to launch a Sword Beam at it, it just barely manages to dodge but loses it's left arm and wing in the process, knocking it's sixth HP bar down to 50%.
Agony of the Feet: The general strategy in the fight against it was to attack it's front feet after it uses it's Breath Weapon, forcing it's head down so they can attack it.
Breath Weapon: As the first dragon monster faced in SAO, it naturally possesses fire breath.
Deadly Gaze: A ability it didn't have in the Beta. Aghyellr can have his emit a light that stuns anyone under Level 20 who looks at it.
Flight: Stands out as the first SAO boss^note chronologically at least to be capable of this, which it wasn't able to in the Beta-Test. It's used to signify when it Turns Red.
Living Macguffin: Similarly to Fuscus, he becomes a target for Kirito's group for reasons outside of being a Floor Boss. That being that dragon blood is the only thing that can cure Nirrnir, Kirito's vampire employer in the Voluptia Casino questline, of poison inflicted on her by an Ardent Snake, and he's the nearest possible source.
Off with His Head!: It's ultimately defeated when Kirito, having just been turned into a vampire by Nirrnir, uses the Sword of Voluptia to launch two Sword Beams at it in a cross shape, the second beam decapitating it.

Floor 10 - Kagachi The Samurai Lord

Kagachi The Samurai Lord

A giant, reptilian creature clad in Samurai armor and wields a Katana.

Disc-One Final Boss: Effectively this, as his defeat will mark the point where Beta-Tester knowledge will lose it's use, as the Beta ended during Floor 10. It will also mark the official end of Kirito's Beater Status.
Everything's Better with Samurai: He's a giant, reptilian creature clad in Samurai armor and wielding a Katana.
Katanas Are Just Better: Comes with the territory.
Reptiles Are Abhorrent: One of the Floor Boss, and allegedly the leader of "Snake Samurai" that plague Floor 10.
Remember the New Guy?: He does not appear until Ordinal Scale as a respawned boss from SAO. Yet all of the characters are familiar with him, despite him never appearing in the story before.
Snake People: His species appears to be that of a humanoid snake, much like most of the monsters on Floor 10.
Snake Whip: He's capable of conjuring a snake-like whip made of energy to attack foes from a distance.
Starter Villain: He's the first respawned SAO Boss to appear in Ordinal Scale that any of the main characters fight.
Sword Beam: He's capable of performing a slash that will send beams of energy at opponents.

Floor 11 - The Storm Griffin

The Storm Griffin

A giant griffin that's apparently capable of manipulating the weather.

Achilles' Heel: Damaging it's wings will prevent it from flying and, in the event that it's in the air, cause it to crash into the ground, making it more vulnerable to close-range attacks. This doesn't make it completely defenseless however, as it will then charge enemies instead.
Blow You Away: With it's giant wings, it can generate strong winds.
Shock and Awe: Along with it's wind, it can summon thunder strikes to attack players with.

Floor 12 - The Strict Hermit

The Strict Hermit

A giant hermit crab creature.

Giant Enemy Crab: Literally a giant hermit crab that serves as a floor boss.
Making a Splash: Its appearances in the video games tend to give it a water based element.
Rapid-Fire Fisticuffs: One of its attacks is a series of rapid strikes with its pincers.
Warm-Up Boss: In Ordinal Scale it's the second SAO floor boss to appear, but it isn't treated as big as a threat as the dragon that came after it.

Floor 18 - The Dire Tusk

The Dire Tusk

A giant pig monster chained to a wall.

Brutish Character, Brutish Weapon: The head of the chain binding him resembles an axe, which he takes to using after breaking free.
Chained by Fashion: He literally starts his fight chained to a wall. Unfortunately, he ends ripping the chain out and using it as a whip.
Full-Boar Action: A giant bipedal boar creature.
Underestimating Badassery: In Ordinal Scale, some players think to take advantage of it being chained up to get some free hits, never accounting that he could simply rip the chain off.

Floor 28 - Waheela the Black Wolf

Waheela the Black Wolf

A giant wolf that has the ability to turn into a black miasma to become invincible and gain greater mobility, at the cost of being unable to attack.

Casting a Shadow: It has the ability to turn into a black mist, granting it fast movement and invincibility. However, it can't attack in this state.
Necessary Drawback: In it's normal form, it can attack players with powerful bites and long-range shadow spike attacks at the expense of being susceptible to damage from melee attacks. In it's mist form, it can avoid attacks and is immune to damage, but it can't deal any back.
Non-Indicative Name: Zig-Zagged. Despite the name, it's fur is actually more of a crimson red color. However, "black" may actually refer to the color of it's mist form.
Savage Wolf: A giant wolf creature that is capable of Casting a Shadow.
Spike Shooter: It's able to use it's shadow abilities to send waves of spikes at it's opponents.

Floor 74 - The Gleam Eyes

The Gleam Eyes

A giant demonic goat creature.

Breath Weapon: One of it's attacks is a purple energy beam from it's mouth.
Dark Is Evil: A large, demonic looking creature with dark blue fur.
Duel Boss: The fight against it ends up turning into this, with Kirito whipping out his Dual Wielding to fight him single-handedly.
Glowing Eyes of Doom: It's in the name.
Katanas Are Just Better: His weapon is a large Zanbatō
Knight of Cerebus: He's so much of a threat that Kirito is forced to actually use his Dual Wielding skill to defeat it after having kept it hidden for so long.
- According to Kirito, he's the first Floor Boss since Floor 67 to kill any players fighting it. Granted this is because the players he killed were severely under-levelled and tired from the journey, but that's still pretty serious in the grand scheme of things.
Sword and Fist: It's shown to attack with both it's giant Zanbato and it's free hand.

Floor 75 - The Skull Reaper

The Skull Reaper

A giant, centipede-like skeleton monster that's capable of One Hit Kills.

Big Creepy-Crawlies: It's effectively a giant centipede made of bones with scythes for pinsers.
Death from Above: Opens up it's fight with an attempt at this, having been clinging to the ceiling before dropping down in a surprise attack.
Dem Bones: It is a giant skeletal centipede like monster.
Draw Aggro: How it's ultimately beaten; while Kirito, Asuna and Heathcliff drew its attention, the rest of the Raid Party flanked it’s sides and attacked it’s side.
Knight of Cerebus: Its murder of 24 players, 10 in the recon team and 14 during the boss fight, causes the Raid Group to hit a Despair Event Horizon due to the possibility of what could be worse than it. This thankfully subsides after Kirito exposes Heathcliff as Kayaba.
One-Hit Kill: It's basic attacks are this, taking out a pair of Tank Players in one swipe of its claws. The only people shown to actually withstand them are Kirito and Asuna, and that's because they blocked them together.

Floor 91 - Dorz’l The Chaos Drake

Dorz'l the Chaos Drake

A massive dragon that, due to SAO being cleared early, was never fought by the Assault Team.

Breath Weapon: Being an enormous dragon, it's only natural that it has this.
Dark Is Evil: A giant, pitch black dragon.
Dragons Are Demonic: His darkly colored appearance and epithet of "Chaos Drake" don't paint it as really friendly...
Draw Aggro: When it spawns in Ordinal Scale, it seems to specifically target Silica. Combined with the fact that it initially spawned as Pina, prompting Silica to approach it, this was likely a trap intended for Silica.
The Unfought: As the Assault Team never went past Floor 75 due to Kirito defeating Kayaba early, Dorz'l was never fought. While they do get a chance to fight it in Ordinal Scale, it ends up escaping and causing them to lose the fight against the Strict Hermit in the process.

Floor 100 - An Incarnation of the Radius

Incarnation of the Radius

The original Final Boss of Sword Art Online.

Barrier Warrior: It has a powerful barrier that prevents attacks from hitting it.
Cool Sword: Carries a white, regal looking sword in her right hand.
Curb-Stomp Battle: When they first encounter her, Kirito’s group consisting of himself, Agil, Liz, Silica and Sinon are quickly overwhelmed by its game-breaking abilities. It’s only when Asuna pulls a Big Damn Heroes and The Cavalry arrives in the form of their allies from ALO and GGO, with Yui giving them their old SAO gear while giving Sinon her GGO gear, that the tables start turning in their favour.
Dishing Out Dirt: It has a move called "Great Separation", which allows it to alter the terrain of its Boss Room to her will.
The Dog Was the Mastermind: Official materials reveals that Ain-Chan, Yuna’s mascot companion, is a deformed version of it.
Dual Wielding: A sword and a spear of all things...
Eye Scream: When Asuna dives in to rescue Kirito and the others, she makes her big entrance by stabbing the boss's eye out.
Healing Factor: It's capable of summoning the Sacred White Tree worshipped by the Forest Elves to heal itself from damage.
Light Is Not Good: Its skin is mostly completely white.
Macross Missile Massacre: Has a Energy Weapon version of this.
Meaningful Name: Its name is a play on Aincrad's full name, "An Incarnating Radius".
One-Man Army: More so than any other boss, where it took literally every available character from every game Kirito had been in to beat it. With Yui having to call in The Cavalry from ALO and GGO to assist.
The Unfought: Kayaba's original plan for Floor 100 involved this boss being removed and replacing it with himself after he turned it into a Death Game. However, in Ordinal Scale, Kirito and his allies are able to fight her as the true Final Boss of SAO.

Field Bosses

Bullbous Bow

A field boss for Floor 2, which needs to be defeated to unlock the Boss Room.

Flunky Boss: Played With. They aren't technically on his side, but the Windwasps that shadow the Bullbous Bow are designed to sting him to make him Turn Red, which requires a party (or, just Kirito and Asuna) to keep them away from him right the main force defeats him.
Meaningful Name: The "Bullbous" in it's name stems from the large, pompadour-like bump on it's head that it uses to attack players.
Small Role, Big Impact: Compared to the Floor Bosses, he's more of a minor threat and the only reason the Clearers deal with him is because he needs to be killed to unlock the Boss Room. However, he drops the the Chakram, which allows Nezha to actually become a combatant and turn the fight against Asterius the Taurus King around, and later on makes him play a vital role against Fuscus the Vacant Collosus.
Turn Red: If the Bullbous Bow is stung by one of the Windwasps, it will turn more aggressive and gain an attack buff.
Use Your Head: As a bull-type monster, it's main method of attack is charging it's enemies head first.

Biceps Archelon

A giant two-headed turtle that blocks off the south of Floor 4.

Boring, but Practical: In it's first phase, it only has three attacks; a bite from both heads, a smack from it's side thins, and a charge move. Not much, but it's greater control in the water makes this a non-issue, and he's capable of capsizing players to make them more vulnerable.
Desperation Attack: When it's HP is in the red, it'll twist it's heads and limbs up agaisnt the shell and start spinning to create whirlind, with the added benefit of increasing it's defence. Fortunately, Kirito's able to use the special battering they were able to make for Tilnel with the Magnatherium Horn to deal the final blow before it perform it.
Mighty Glacier: It has the ability to capsize players and leave them vulnerable and it's so powerful that even Asuna Chivalric Rapier +5 can't deal much damage to it, but this comes at the expense of it being very slow.
Sturdy and Steady Turtles: A giant, ancient two-headed turtle with powerful defense.

Zehgi the Flame Caller

A field boss for Floor 11. In Ordinal Scale, it's summoned by Eiji to fight Fuurinkazan.

An Arm and a Leg: It's Implied that his legs are easy to cut off, leaving it vulnerable. Klein does this when it ambushes Fuurinkazan.
Breath Weapon: One of it's attacks appears to be some kind of Fire Breath. After delivering a Curb-Stomp Battle to him, Eiji ensures that he loses his SAO memories by lifting him up and making he gets hit by it.
Carry a Big Stick: It's weapon was a massive club.
Draw Aggro: It's apparently easy to do this with, with Dynamm mere insulting it to get it's attention.
Playing with Fire: Played With. Despite it's name, it's only flame-related move appears to be a Breath Weapon.

Ruthless Warder Chief

A dungeon boss of Floor 40.

Achilles' Heel: Achilles Knees in this case, which serve as his weak-point.
Carry a Big Stick: He wields a one-handed club resembling a Kanbato.
Kick Them While They Are Down: It possesses the "Bullying" algorithm, which makes it prioritize players who are either knocked down or debuffed, ignoring normal hate values.
Muscles Are Meaningful: He's muscular to the point of having visible veins on it's arms and legs
Simple, yet Awesome: It's attack patterns are fairly simple, relying largely on narrow and wide-ranged Sword Skills. However, since he's fought in a narrow passageway, it still makes him very dangerous.

Feral Warder Chief

A dungeon boss of Floor 40, that's weaker than the Ruthless Warder Chief but no less a threat.

Brutish Character, Brutish Weapon: In contrast to it's stronger counterpart, it instead wields an axe.
Flunky Boss: While he's weaker than the Ruthless Warder Chief, his variation of Turn Red also summons a bunch of minions to assist him.
Malevolent Masked Man: Along with with it's helmet, it wore a cloth mask with a smiling, sharp-toothed mouth.
Moveset Clone: The fight against it initially went well since Eiji recognized it's patterns as also belong to the more powerful Ruthless Warder Chief. Unfortunately, he differentiated himself from his more powerful counterpart by being a Flunky Boss.
Unwitting Instigator of Doom: Similarly to Illfang with Diaval above, his (or more accurately, his minion's) murder of Yuna has long-lasting consequences, as it led to Shigemura's attempt to bring her back using his Augma, which could have possibly killed most of the SAO Survivors in the process.

The Geocrawler

A giant, armored worm creature located outside of a NPC village on Floor 56 that proves difficult to defeat.

Boss Room: Another part of it's difficulty is the location where it's fought, a narrow mountain corridor that makes being able to attack it's weakness much harder.
Curb-Stomp Battle: Like Wythege above, it's on both ends of this. While it thankfully takes no lives in the time spent dealing with it, every attempt at fighting it has ended in the Clearers being forced to retreat, due to it being mostly Nigh-Invulnerable and it's only weak-spot, it's underbelly, being hard to reach. However, after it's discovered that a lullaby sang by the village girl "Lulu" can put it to sleep, it's unable to do anything as the Clearers hack it to death.
Nigh-Invulnerable: The main reason it's such a threat. Asuna notes during the strategy meeting that it's repelled any attacks from slash, thrust and blunt attacks used against it, while it's only weak point is extremely hard to attack.
Sand Worm: The Geocrawler is some manner of giant worm monster that's as tall as a house and many times as long.
Small Role, Big Impact: In the pre-Progressive Canon, it's the fight against the Geocrawler that starts off Asuna's growing feelings for Kirito, since his willingness to stand up to her over her NPC Bait strategy, her subsequent loss against him in a duel, and witnessing how he's not letting being stuck in Aincrad stop him from living kickstarts her attraction to him and leads to their marriage 8 months after-the-fact. The exact role he has in the Progressive canon in light of the Retcon of Kirito and Asuna knowing each other personally since Floor 1 is yet unconfirmed.

Quest/Event Bosses:

Nicholas the Renegade

An event boss resembling a deformed Santa Claus, who's rumored to drop a revival item.

Bad Santa: His entire gimmick is being an evil revenant with the appearance of Santa Claus.
Carry a Big Stick: He wields a giant club in combat.
Curb-Stomp Battle: The fact Kirito is able to solo him on his own shows he's substantially weaker than a Floor Boss.
Killed Offscreen: Kirito's actual victory over it is not shown onscreen, but the fact he attained the boss drop is proof that he beat it.
Santabomination: Essentially he is if Santa was a deranged zombie.

X'rphan the White Wyrm

A boss found at the top of the West Mountain on Floor 55, rumored to be guarding a high-grade crafting material

An Ice Person: Living on a snowy mountain, X'rphan employs a number of ice based abilities, including a Breath Weapon and creating wind currents with it's wings to send snow at it's enemies.
Blow You Away: It's able to beat it's wings with enough force to create wind currents to move the snow.
Right for the Wrong Reasons: The rumors turn out to be correct that it is in the possession of a rare crafting material. What isn't known is that it also makes it, sustaining itself on the crystals on the mountain and... letting nature takes its course.
Solid Gold Poop: His excrement serves as a rare crafting material, which Kirito and Liz acquire to create the Dark Repulsor.

Alfheim Online

New Aincrad

Floor 8 - Wadjet the Flaming Serpent

Wadjet the Flaming Serpent

A giant snake-woman who burned down the forest of Floor 8.

Boss-Arena Idiocy: Her Boss Room contains a number of mirrors which can be used to redirect her Instant Kill Ray back at her, which will weaken her and deal severe damage.
Cast from Hit Points: Wadjet is often surrounded by a shieling aura made of flames. However, whenever she uses a fire-element skill the aura will weaken, giving players the opportunity to damage her.
Destroyer Deity: Implied. Wadjet is the named after a Goddess of fire in Egyptian mythology who took the form of a snake, and the Floor 8 of New Aincrad, which in the original was a lush green forest, is a forest that was severly burnt, which is heavily hinted to be her doing.
The Dreaded: According to the narration, Wadjet has become something of this to the New Aincrad Clearing force by the time of "A New Day".
Flunky Boss: Wadjet is capable of summoning fiery minions.
Logical Weakness: As a giant, flaming snake creature, she's naturally weak to Water-element moves.
Magic Knight: Her attacks are largely fire-based, but it also possesses four swords in each that allow to deal powerful physical attacks.
Multi-Armed and Dangerous: The woman part of Wadjet possesses four arms, each one holding a large sword.
Playing with Fire: As it's name suggests, her moves are largely fire-based in nature.
Reptiles Are Abhorrent: Wadjet is a giant cobra-like creature, with the visage of a four-armed woman beneath the the head.

Floor 27 - The Four-Armed Giant

The Four-Armed Giant

A giant, two-headed, four-armed monster.

Attack Its Weakpoint: It's weakness is the gem on it's neck that it'll occasionally protect with it's arms. Yuuki uses Mother's Rosario on it to defeat the boss.
Chain Pain: It's other arms are holding a long set of chains that it can use for a sweeping attack.
Counter-Attack: It has access to a unique stance that not only nullifies damage, but reflects it back.
Dual Wielding: Two of it's arms are holding a pair of pointed wooden hammers.
Mighty Glacier: It has powerful, hard-hitting attacks, but is very slow. It also makes it a point to defend it's weakpoint.
Multi-Armed and Dangerous: Basically it's entire schtick; it's got four arms that are holding hammers and chains, that they can use for both attacking and for defending it's weak point.
Multiple Head Case: It has two heads.
Poisonous Person: One of it's attacks is a poison Breath Weapon.
Red Eyes, Take Warning: Both it's heads have glowing red eyes.
Turns Red: Progressively. The more damage it attacks, the more aggressive it's attack patterns will become, even being able to whip out a uniuqe 8-hit Sword Skill using all it's weapons.

Other Bosses

Black and Gold Minotauruses

A pair of minotaur monsters that appear in Thrym's palace, wielding axes and possessing high resistance against physical and magic attacks respectively.

Anti-Magic: The Black and Gold Minatauruses have high resistances against magical and physical damage respectively. This puts Kirito's party at a disadvantage against the Gold one due to their only mages being Asuna and Leafa, both of whom are Magic Knights and not full-on mages, but also allows them to deal a Curb-Stomp Battle against the Black one once they manage to defeat the Gold one.
Brutish Character, Brutish Weapon: The both of them wield large axes when in combat.
Curb-Stomp Battle: Due to his vulnerability to physical attacks, the fight against the Black Minataurus is over fairly quickly.
Logical Weakness: To work around the Gold Minotaur's Physical Resistance, the group Zerg Rushes him with Sword Skills with Elemental Properties.
One-Hit Kill: The both of them possess a skill that instantly kills players. Thankfully, it's very easy to dodge.
Tag Team: Effectively how they function; the party takes on one of them at a time, and if one suffers enough damage, then it will take to the back and assume a meditative pose to heal while it's partner fights the players. This forces the party to assume a physical/magic based stance system due to their respective resistances.

Characters / Sword Art Online - Bosses

Sword Art Online

Floor Bosses

Illfang the Kobold Lord

The Tauruses

Nato the Colonel Taurus

Baran the General Taurus

Asterius The Taurus King:

Nerius The Evil Treant

Wythege the Hippocampus

Fuscus the Vacant Colossus

The Irrational Cube

Aghyellr the Igneous Wyrm

Kagachi The Samurai Lord

The Storm Griffin

The Strict Hermit

The Dire Tusk

Waheela the Black Wolf

The Gleam Eyes

The Skull Reaper

Dorz'l the Chaos Drake

Incarnation of the Radius

Field Bosses

Biceps Archelon

Zehgi the Flame Caller

Ruthless Warder Chief

Feral Warder Chief

The Geocrawler

Quest/Event Bosses:

Nicholas the Renegade

X'rphan the White Wyrm

Alfheim Online

New Aincrad

Wadjet the Flaming Serpent

The Four-Armed Giant

Other Bosses

Previous

Index

Next

Characters / Sword Art Online - Bosses

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Sword Art Online

Floor Bosses

Illfang the Kobold Lord

The Tauruses

Nato the Colonel Taurus

Baran the General Taurus

Asterius The Taurus King:

Nerius The Evil Treant

Wythege the Hippocampus

Fuscus the Vacant Colossus

The Irrational Cube

Aghyellr the Igneous Wyrm

Kagachi The Samurai Lord

The Storm Griffin

The Strict Hermit

The Dire Tusk

Waheela the Black Wolf

The Gleam Eyes

The Skull Reaper

Dorz'l the Chaos Drake

Incarnation of the Radius

Field Bosses

Biceps Archelon

Zehgi the Flame Caller

Ruthless Warder Chief

Feral Warder Chief

The Geocrawler

Quest/Event Bosses:

Nicholas the Renegade

X'rphan the White Wyrm

Alfheim Online

New Aincrad

Wadjet the Flaming Serpent

The Four-Armed Giant

Other Bosses

Previous

Index

Next