History Characters / TheBindingOfIsaacFinalBosses

* {{Superboss}}: In ''Four Souls'', Delirium is the only boss who doesn't grant a soul upon defeat, instead allowing the victor to gain two treasure cards. He is also one of the harder bosses despite being considered a "normal" one, having stats on par with with a Mega Boss (Satan, The Lamb, etc.) and giving other monsters a higher dice roll. ''Requiem'' somewhat rectifies this by putting him in said Mega[[note]]now called Epic[[/note]] Boss tier, though he still does not grant souls.

* {{Superboss}}: In ''Four Souls'', Delirium is the only boss who doesn't grant a soul upon defeat, instead allowing the victor to gain two treasure cards. He is also one of the harder bosses despite being considered a "normal" one, having stats on par with with a Mega Boss (Satan, The Lamb, etc.) and giving other monsters a higher dice roll.

** In ''Repentance'', many of the redesigned bosses gaining extra eyes in unnatural places (Duke of Flies' mouth, Lokii's brain, Fistula's holes, just to name a few).

* BossBonanza: They collectively have a total of 7800 HP[[note]]Ultra War, Ultra Famine, and Ultra Death each have 2,000 HP while Ultra Pestilence has 1,800 HP[[/note]], which is even more than Hush and Mega Satan. And they're the ''in-between'' bosses between Dogma and The Beast. The only reprieve Isaac has is each fight being treated as a wave, just like Challenge Rooms and the game's own BossRush, so any room-clearing effects will proc here.

* {{Facepalm}}: Ultra Death facepalms in the background when the three other Harbingers die (or more specifically, when Ultra War dies, who directly precedes Ultra Death).

* ShowsDamage: As she takes more and more punishment, she starts bleeding, losing teeth, eyes, and her horns. This is especially noticeable during the third and final phase.

[[/folder]]

* BattleThemeMusic: "''[[https://www.youtube.com/watch?v=ULbzWE_tC5M Revelations 13-1]]''". The boss theme is segmented so that it fits each of the Ultra Harbingers specifically until it reaches the Beast proper, but for all intents and purposes, it's the Beast's proper boss theme. The segment corresponding to it involves a lot more demonic chanting and distorted guitar.

* EasterEgg: Hitting Dogma with the magnetism effect of Lodestone will cause his static to become fuzzy, like the magnet was interfering with the TV's signal.

* KnifeNut: One of its attacks has it pulling out and throwing a gigantic knife.

* AnthropomorphicPersonification: Of the mental breakdown that Isaac is going through as he's suffocating in the chest. Delirium can rapidly shift between the forms of bosses previously encountered in the current run, and rarely ever sits still while spraying bullets everywhere. And during his death animation, the screen gets covered with static as moments from earlier in the run are replayed. All of this represents how Isaac's mind is spiraling inward as he dies within the chest, being a rather extreme take on the MyLifeFlashedBeforeMyEyes trope.

* TheGambler: His primary attack depends on the outcome of a slot machine. Although it's not ''that'' much of a gamble, since every outcome is pretty terrible for you. You're just hoping that he gets one of the ''less'' terrible ones.

-->'''''And the beast which I saw was like unto a leopard, and his feet were as the feet of a bear, and his mouth as the mouth of a lion: and the dragon gave him his power, and his seat, and great authority.'''''

* GiantFootOfStomping: Her main method of direct attack. Her Red Champion variant takes it UpToEleven — her stomping becomes her main attack[[note]]her summoning is replaced by a spread shot[[/note]] and is executed at roughly twice the speed.

** Taken UpToEleven in ''Repentance'', with many of the redesigned bosses gaining extra eyes in unnatural places (Duke of Flies' mouth, Lokii's brain, Fistula's holes, just to name a few).

* TimedMission: Played with. If you want to guarantee access to the Void and thus to Delirium, you have to beat Hush, which means you need to beat It Lives before the 30 minute mark (or have Mama Mega! on that floor). Howeve, the portal to the Void has a chance to spawn after beating Mom or any subsequent boss, increasing as you go further. Mega Satan has a 50% chance at best. He's also the only boss for whom completion is tracked even on victory laps, however, so one valid strategy is to take your time gathering items on the first run, defeat The Lamb, and then [[CurbStompBattle speedrun through the victory lap with your items]] to reach Hush.

** In ''Repentance'', it supposedly loses this role to Dogma and The Beast;[[note]]you actually have to beat Hush 3 times to unlock the alternate path and then have to beat Mother on said alternate path at least once to even unlock the ability to fight the Beast, as opposed to defeating Hush once[[/note]] though it is possible to defeat both of those bosses before Delirium. However, Delirium's ending is still confirmed to be the canonical one, making it remain the true final challenge battled in the story as a whole.

* WoobieDestroyerOfWorlds: Implied with how her voice sounds and the context for her existence. Isaac kills her with the assembled Knife Pieces after finishing her in the Mausolem/Gehenna, and now as Mother, she's attacking again out of despair and heartbreak over her son actually killing her. She even has a little "heartbreak" icon next to her name in the VersusCharacterSplash.

Dogma is the first of the two bosses of TheVeryDefinitelyFinalDungeon, Home. After a flashback sequence where Isaac recalls the fallout between his parents' relationship, he has a nightmare about the televangelist sermons that drove his mother to madness. Approaching the TV brings forth this thing, an angelic fetus made of static, representing the demented fundamentalism that drove Mom into her religious fervor and Isaac into his suicidal guilt.

* DiscOneFinalBoss: Mom's Heart normally appears at the end of the Womb, but shows up two chapters in the alt route, immediately after Mom herself, as its regular place is taken by Mother.

* FallenAngel: The OG in all of his "glory". Tellingly, he and The Fallen are the only demonic enemies Isaac encounters[[note]]If you don't count Fallen Uriel/Gabriel[[/note]] who have visibly angelic wings.

* ShesGotLegs: Inverted. The game gives us a detailed sprite of Mom's leg and it's textbook FanDisservice.

* SmallRoleBigImpact: As you unlock more of the game, Mom's role as a final boss becomes more and more pushed to the side. However, your actions after defeating her still determine the course your run will take:

Defeating Mom once unlocks the Womb in subsequent playthroughs. At the end of the Womb lies Mom's Heart, which, summons enemies like Mom does. Defeating Mom's Heart reveals a Chest with something special inside. But once it's beaten enough times, it will become "It Lives!", which is Isaac as a fetus for some odd reason.

* GiantFootOfStomping: Her main method of direct attack. Her Red Champion variant takes it UpToEleven — her stomping becomes her only main attack at twice the speed.

** Eraser[[note]]permanently removes an affected enemy from the run, which includes bosses if their health is low enough[[/note]] can also potentially one-shot it, assuming you used it to erase a boss prior.

* PokemonSpeak: Her only voice lines, outside of VoiceGrunting, is her screaming ISAAC!

[[caption-width-right:192:'''[[MadnessMantra BAD BAD BAD]] [[ItsAllMyFault I'M THE DEVIL]]''']]

The Beast of the Apocalypse, the Mother of Harlots, heralded by the Four Horsemen. Repentance's TrueFinalBoss ([[GrandFinale and by extension]] [[FinalBattle the series as a whole]]), The Beast challenges Isaac after his victory over Dogma.

[[caption-width-right:192:'''BAD BAD BAD I'M THE DEVIL''']]

[[caption-width-right:192:T̶̠̈H̸̨͘Ẹ̸͛ ̵̥͘E̸͎͛N̸̮͒D̷̗͆]]

** Amusingly, if it's in the form of "ghost" boss (such as The Haunt) and it's at less than half of its health, it is ''not'' immune to OneHitKill effect that Vade Retro has on ghost enemies.

* BulletHell: Fires bullets in all directions, and fires at you if you hit him. Having a high-fire rate can backfire horribly.

* LosingYourHead: During the second phase of the battle, The Lamb's head detaches from its bod. However, it clearly isn't fatal.

* InterfaceScrew: The only boss [[note]]Besides the Mask Of Infamy in the original, as well as The Ultra Harbingers and The Beast[[/note]] who doesn't have a health bar, in either form. Averted if you have the Spider Mod item, which gives him a Spider Mod health bar.

* TheGambler: His primary attack depends on the outcome of a slot machine. Although it's not ''that'' much of a gamble since every outcome is pretty terrible for you. You're just hoping that he gets one of the ''less'' terrible ones.

All {{spoiler}}s are [[Administrivia/SpoilersOff unmarked]] from here on out. Proceed at your own caution!

* BonusBoss: In ''Four Souls'', Delirium is the only boss who doesn't grant a soul upon defeat, instead allowing the victor to gain two treasure cards. He is also one of the harder bosses despite being considered a "normal" one, having stats on par with with a Mega Boss (Satan, The Lamb, etc.) and giving other monsters a higher dice roll.

* BossBonanza: They collectively have a total of 7800 HP[[note]]Ultra War, Ultra Famine, and Ultra Death each have 2,000 HP while Ultra Pestilence has 1,800 HP[[/note]], which is even more than Hush and Mega Satan. And they're the ''in-between'' bosses between Dogma and The Beast.