Delirium

Base HP	Stage HP
10000	0

Ingame Appearance

Entity ID
412.0

Found In
Boss

Dropped Items
Final Boss Chest

Delirium is a boss added in The Binding of Isaac: Afterbirth †. It is the main boss of The Void, and the final boss of Ending 20.

Behavior

• Delirium will teleport around the room, sending out an array of White projectiles and Green projectiles that explode like Ipecac.
• Its most notable (and dangerous) attack is that it will transform into bosses previously encountered during the run, including a few of the "final" bosses (Mom, It Lives, etc.).
  • While transformed, it will attack with its White and Green projectiles along with the attacks of the boss it transformed into.
  • When it transforms into a boss, Delirium retains its own health, not the health of the boss it transformed into.
  • The attacks of the transformed boss are dependent on Delirium's current HP. For example, if Delirium transforms into War while at <50% HP, it will be horseless and run at Isaac.
  • It can rarely transform into two instances of the same boss.
  • Whether it turns into Champion variants or regular variants is random and does not depend on which variant was previously defeated. For instance, it can turn into Dark Greyish Green Champion Gurdy, even if the regular Gurdy was the defeated variant, and vice-versa.
  • It is unable to properly transform into Hush's true form. In order for this to happen, very few bosses must be encountered in the run, and many of Hush's attacks will not work properly. The sprite is also unfinished.
    • With Delirious, Hush can be summoned, but it has chance of happening if it is used many times in quick succession in a same room, which is only possible via cheats or the Debug Console.
  • The only boss added in Repentance that Delirium can properly transform into is Baby Plum.
    • While Delirium technically can transform into the majority of bosses added, only Baby Plum has a unique skin.
• Occasionally, it will return to its main form to shoot the White projectiles more aggressively and to shoot the Green projectiles more often.
• Progressively, it will alternate through each form faster and become more aggressive.

Upon defeat, the screen will start to glitch and fill with static while short moments from the current run are played, and the room will switch between different environments, ending with a Chest layout. After being defeated, Delirium will burst into blood and drop a Final Boss Chest, playing Ending 20.

Damage Scaling

Damage scaling is an unclear mechanic introduced by Nicalis in The Binding of Isaac: Afterbirth to provide a more challenging experience to the players, enabling some enemies to retaliate against high damage attacks by deploying an "armor" of a sort to greatly reduce the amount of damage taken. Further details and an in-depth explanation may be found here.

Delirium ONLY has damage scaling while transformed, not while in their main form.

Notes

• Delirium is immune to Chaos Card.
• Plan C is ineffective against Delirium. While it does kill Delirium, because its death animation is longer than 3 seconds, Isaac will still be killed first.
  • However, it works with Lazarus' Rags as they both revive Isaac on the spot. Note that the character will be turned into Lazarus.
  • Soul of Lazarus and Inner Child also revive Isaac in the same room he died in.
• Most entities that are considered to be bosses by the game (usually identified by ones that add the boss health bar to the screen) are marked as bosses that Delirium can transform into.
  • The Seven Sins are exceptions to this.
  • Delirium can transform into either form of Satan.
  • When transformed into the Gurglings or the Turdlings, it will only appear as one instead of two.
  • When transformed into The Headless Horseman, it transforms into either the head or the body, but it doesn't transform into both.
  • Each size of Fistula and Teratoma count as their separate boss which Delirium can transform into just like any other boss.
  • This also results in many bugs due to unaccounted for transformations. These can be viewed in the bugs section of this page.
  • When transformed into a boss that has multiple segments, the extra segments can be killed. The head, however, cannot.
  • This also applies to Gemini - Suture can be killed but Contusion cannot.
  • All parts of Fistula and Teratoma can be killed (though they have much greater health than normal), and the room will remain empty until Delirium transforms again. Even though the segments have been killed, Delirium itself has not been killed.
• When transformed into two instances of the same boss (like Lokii or Sisters Vis), one of them can be killed but the other cannot.
• Delirium's Mom form only stomps and does not spawn enemies.
• If Delirium transforms into Gemini then undergoes another transformation, Suture doesn't disappear. Instead, he will come after the player like the original version does after Contusion is killed.
• When turning into certain multi-phase bosses (such as Isaac), Delirium copies the phase that that boss would be at, given their current health percentage.
• If Delirium transforms into The Lamb's second phase then undergoes another transformation, the body doesn't disappear and can be killed, just like the original Lamb's body.
  • However, Delirium can also transform into the Lamb's body on its own. If this happens, the body will disappear when Delirium transforms again.

Gallery

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  Delirium in-game.

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  Delirium as Dingle/Dangle.

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  Delirium as Gurglings.

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  Delirium as Little Horn.

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  Delirium as Turdlings.

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  Delirium as Rag Man.

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  Delirium as Famine.

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  Delirium as Gemini.

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  Delirium as Steven.

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  Delirium as Blighted Ovum.

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  Delirium as The Duke of Flies.

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  Delirium as The Husk.

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  Delirium as Larry Jr.

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  Delirium as The Hollow.

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  Delirium as The Haunt.

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  Delirium as The Forsaken.

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  Delirium as Widow.

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  Delirium as The Wretched.

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  Delirium as Pin.

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  Delirium as The Frail.

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  Delirium as Monstro.

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  Delirium as Monstro II.

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  Delirium as Gish.

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  Delirium as Fistula.

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  Delirium as Teratoma.

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  Delirium as Baby Plum.

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  Delirium as Gurdy Jr.

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  Delirium as Rag Mega.

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  Delirium as Gurdy.

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  Delirium as Big Horn.

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  Delirium as Pestilence.

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  Delirium as Polycephalus.

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  Delirium as The Stain.

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  Delirium as Chub.

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  Delirium as C.H.A.D.

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  Delirium as Carrion Queen.

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  Delirium as Mega Fatty.

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  Delirium as The Cage.

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  Delirium as Dark One.

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  Delirium as The Adversary.

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  Delirium as Peep.

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  Delirium as The Bloat.

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  Delirium as Mega Maw.

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  Delirium as The Gate.

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  Delirium as Brownie.

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  Delirium as Mask of Infamy.

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  Delirium as Sisters Vis.

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  Delirium as War.

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  Delirium as Loki.

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  Delirium as Lokii.

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  Delirium as Blastocyst.

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  Delirium as Scolex.

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  Delirium as Death.

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  Delirium as Conquest.

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  Delirium as Daddy Long Legs.

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  Delirium as Triachnid.

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  Delirium as Mr. Fred.

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  Delirium as Mama Gurdy.

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  Delirium as The Matriarch.

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  Delirium as The Fallen.

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  Delirium as The Headless Horseman.

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  Delirium as Krampus.

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  Delirium as Uriel.

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  Delirium as Gabriel.

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  Delirium as Mom.

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  Delirium as Mom's Heart.

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  Delirium as It Lives.

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  Delirium as Satan.

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  Delirium as Isaac.

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  Delirium as ???.

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  Delirium as The Lamb.

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  Delirium as Mega Satan.

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  Delirium as Hush (First phase).

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  Delirium defeated.

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  Delirium's main Form on Isaac's last will.

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  A frame of Delirium's death animation, showing a faded sprite of Isaac.

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  Delirium as Hush (unused and unfinished).

Unlockable Achievements

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  Delirious - Defeat Delirium.

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  Lil Delirium - Defeat Delirium for the 1st time.

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  D Infinity - Defeat Delirium as Isaac.

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  Eucharist - Defeat Delirium as Magdalene.

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  Silver Dollar - Defeat Delirium as Cain.

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  Shade - Defeat Delirium as Judas.

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  King Baby - Defeat Delirium as ???.

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  Dull Razor - Defeat Delirium as Eve.

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  Bloody Crown - Defeat Delirium as Samson.

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  Dark Prince's Crown - Defeat Delirium as Azazel.

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  Compound Fracture - Defeat Delirium as Lazarus.

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  Eden's Soul - Defeat Delirium as Eden.

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  Holy Card - Defeat Delirium as The Lost.

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  Euthanasia - Defeat Delirium as Lilith.

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  Crooked Penny - Defeat Delirium as Keeper.

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  Void - Defeat Delirium as Apollyon.

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  Book of the Dead - Defeat Delirium as The Forgotten.

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  Star of Bethlehem - Defeat Delirium as Bethany.

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  Suplex! - Defeat Delirium as Jacob and Esau.

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  Spindown Dice - Defeat Delirium as Tainted Isaac.

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  Hypercoagulation - Defeat Delirium as Tainted Magdalene.

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  Bag of Crafting - Defeat Delirium as Tainted Cain.

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  Dark Arts - Defeat Delirium as Tainted Judas.

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  IBS - Defeat Delirium as Tainted ???.

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  Sumptorium - Defeat Delirium as Tainted Eve.

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  Berserk! - Defeat Delirium as Tainted Samson.

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  Hemoptysis - Defeat Delirium as Tainted Azazel.

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  Flip - Defeat Delirium as Tainted Lazarus.

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  Corrupted Data - Defeat Delirium as Tainted Eden.

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  Ghost Bombs - Defeat Delirium as Tainted Lost.

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  Gello - Defeat Delirium as Tainted Lilith.

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  Keeper's Kin - Defeat Delirium as Tainted Keeper.

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  Abyss - Defeat Delirium as Tainted Apollyon.

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  Decap Attack - Defeat Delirium as Tainted Forgotten.

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  Lemegeton - Defeat Delirium as Tainted Bethany.

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  Anima Sola - Defeat Delirium as Tainted Jacob.

Trivia

• Delirium is Isaac's manifestation of the "white light at the end of the tunnel" where the entire history of his life flashes before his eyes, moments before Isaac's death.
  • This is reflected by Delirium's death animation and its ability to shapeshift into different bosses you previously encounter.
• Delirium is one of only two enemies immune to Chaos Card, the other being The Beast.
• Killing Delirium in a daily challenge counts as winning it. However, this does not reward any unique bonus points.
• Unlike other completion marks, defeating Delirium does not add a mark to the post-it note. Instead, the note will become tattered (with blood on Hard mode).
• If no other bosses have been encountered during the run, Delirium will be unable to transform.
  • This is normally impossible as you have to defeat at least one boss, even if extremely lucky. Use floor skips such as Ehwaz or We Need to Go Deeper! until chapter 3. After the fight with Mom, Isaac has a 5% chance of teleporting to The Void, but only if Isaac has 10+ tear damage or 20+ items. Then, you must find Delirium without encountering any other bosses.
• There was a glitch in the original version of The Binding of Isaac: Afterbirth † which caused Delirium's main form to lack an idle animation. This was soon patched.
• In the game files, there is an unused Delirium transformation of Ultra Greed with a beard.
  • Delirium can transform into Ultra Greed if he is encountered, but this is normally impossible as the bosses never appear in the same game mode.
• Every time Delirium transforms into another boss, it adds onto the encounters counter in the Bestiary.
• If Delirium transforms into a Champion boss that doubles itself (i.e. Red Champion Monstro), one of them will have Delirium's skin while the other will have the original boss' skin.
  • In this case, the one with the original boss' skin can be killed, but the one with Delirium's skin cannot.
• If Delirium transforms into Mom as soon as the battle starts, it will stomp in the center of the room regardless of Isaac's position, similar to how the original Mom always starts her battle by stomping in the center of the room.
  • Similarly, If Delirium transforms into Mom's Heart/It Lives as soon as the battle starts, it will be accompanied by two Eyes in the same position as they are when they accompany the original Mom's Heart/It Lives at the start of its battle.
• Prior to Booster Pack #5, Delirium could turn into a Lil' Haunt.
  • Also, if it transformed into Black Champion Brownie when at low health, It would spawn two Dank Squirts like the original boss would and die before the health bar actually fully depleted, without playing its death animation. This no longer happens because Delirium's Brownie form (normal and Black Champion) no longer transitions into the second phase (turning into a weakened Dangle or leaving two Dank Squirts, respectively).
• Delirium uses the exact same sprite for both its Dingle and Dangle forms.
• If Delirium transforms into Mega Fatty and performs the vomit attack, it will attract its White and Green projectiles towards it.
• The only bosses Delirium can't normally transform are Ultra Greed, Ultra Greedier, Hush (it can, but via cheats or bugs) and any other Repentance boss except for Baby Plum.
  • Delirium can even transform into the hidden incomplete Skinless Hush boss, which will simply not move and do basic attacks.

Bugs

Bug!	If Delirium transforms into an enemy like Chub with multiple hitboxes, the game may crash if one of the secondary hitboxes is hit by Chaos Card.

Bug!	Delirium can transform into Fallen Uriel and Fallen Gabriel, but they do not have unique Delirium skins.

Bug!	If Delirium transforms into Mega Satan, the sprites will bug out. It can attack normally, but the sprite may not be visible/half-visible/only showing the hands.

Bug!	On Isaac's last will, Delirium will be shown in its current form rather than its main one. Sometimes it will show his main form, even if Isaac is killed by a different form.

Bug!	Delirium can sometimes deal unavoidably glitched damage. For example, when transformed into Mom, Isaac can sometimes take damage before Mom's leg stomps.

Bug!	Sometimes, when Delirium transforms into a segmented boss, its health will appear to be lower than it is. This is usually purely visual and returns to normal whenever it transforms again, though it may not return to normal.

Bug!	If Delirious is used to spawn Hush, Delirium will be able to transform into Hush.