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Delirium (デリリウム Deririumu) is the final boss at the end of The Void chapter. It is added to the Afterbirth † DLC. It is assumed to be one of the true final bosses appearing in final chapters of the game, along with Mega Satan.

Description Description

Delirium's true self is a gigantic, white skull-resembled entity sporting large eye-sockets consisted with black eyes and yellow iris. Its mouth sport long vein-like "stitches", similar to Hush.

From all forms Delirium takes, each are identical to respective bosses from the previous chapters, except with Delirium's own colors, including white colors, yellow eyes, and a "melting" mouth.

Blast Behavior

Delirium can teleport randomly around the room, and send out wave of white projectiles.

Unlike other bosses, Delirium has a unique ability to shape-shift into all bosses from previous chapters, including both normal, posthumous and alternative types, as well as final bosses. However, Delirium does not shape-shift into forms based on minibosses (such as Seven Deadly Sins, Krampus, etc.), although it still can take forms based on the angels. Delirium can also transform into Lil' Haunt, the only monster it can turn into that is not a boss. All various forms Delirium shifts into are listed in the table -

Form Description
Delirium-Blue-Baby
Blue Baby
Wave of tears
Spawn Attack Flies, Pooters, Eternal Flies
Delirium-Adversary
The Adversary
Earthquakes
Spawn Spiders
Brimstone-beam
Delirium-Big-Horn
Big Horn
Summon dark balls
Throw troll bombs
Clawing
Delirium-Blastocyst
Blastocyst
Leaping, ring of blood-shots
Delirium-Blighted-Ovum
The Blighted Ovum
Contusion: Follow, leaving red creep
Suture: Brimstone-beam
Delirium-Bloat
The Bloat
Brimstone-beam
8-way blood-shots
Bloat Eyes
Delirium-Brownie
Brownie
Spawn Corn Mines, Brownie Corns
Leave brown creep
Hopping
Delirium-Cage
The Cage
Leaping, do earthquakes
Spawn Vises
Delirium-Carrion-Queen
Carrion Queen
Ramming
Spawn red poop
Low health: Bouncing
Delirium-CHAD
C.H.A.D.
Ramming
Spawn Suckers
Delirium-Chub
Chub
Ramming
Spawn Chargers
Delirium-Conquest
Conquest
Dash, with clones
Holy beams
4-way psychic blood-shots
Delirium-Daddy-Long-Legs
Daddy Long Legs
Spawn Spiders
Stomping, 8-way blood-shots
Delirium-Dangle
Dangle
Corn-shots
Spawn Brownie Corns
Ramming, leave brown creep, spawn Corn Mines
Delirium-Dark-One
Dark One
Dash
Ring of bullets
Brimstone-beam
Delirium-Death
Death
Summon scythes
Slow-time
Death solo: Spawn Knights
Pony: Dash
Delirium-Dingle
Dingle
Poop-shots
Spawn Dips
Ramming
Delirium-Duke-of-Flies
The Duke of Flies
Spawn Attack Flies
Delirium-Fallen
The Fallen
4-way Brimstone-beams
Blood-shots
Follow while ramming
Division
Delirium-Famine
Famine
Dash
Spawn Pooters
2nd phase: Blood-shots
Delirium-Fistula
Fistula
Division
Spawn Chargers
Delirium-Forsaken
The Forsaken
Spawn Bonies
Brimstone-beams
Delirium-Frail
The Frail
Hide underground
Jump directly to the player
4-way blood-shots
2nd phase: Brimstone-beam
Delirium-Gabriel
Gabriel
4-way light beams
Ring of blood-shots
Spawn Angelic Babies
Delirium-Gate
The Gate
Spawn Leapers
Brimstone-beam
Delirium-Gemini
Gemini
Contusion: Follow
Suture: Blood-shot
Delirium-Gish
Gish
Explosive shot
Spawn Clots
Delirium-Gurdy
Gurdy
Spawn Attack Flies, Pooters, Sacks
Blood-shot
Delirium-Gurdy-Jr
Gurdy Jr.
Dash
Blood-shot
Delirium-Gurgling
Gurgling
Dash, spawn Attack Flies
Delirium-Haunt
The Haunt
Blood-shot
Brimstone-beam
Delirium-Headless-Horseman
Headless Horseman
Head: Dash
Body: Explosive shot
Delirium-Hollow
The Hollow
Move around aimlessly
Contact damage
Delirium-Hush-1
Hush (1st phase only)
Wave of tears
Spawn Attack Flies, Pooters, Eternal Flies
Delirium-Husk
The Husk
Spawn Spiders
Delirium-Isaac
Isaac
Wave of tears
Holy beams
2nd phase only: Spawn Babies
Delirium-It-Lives
It Lives
Appear with Eyes
Wave of blood-shots
Delirium-Krampus
Krampus
4-way Brimstone-beams
Blood-shots
Delirium-Lamb
The Lamb
Wave of blood-shots
Explosive shot
2nd phase: Ramming
Delirium-Larry-Jr
Larry Jr.
Move around aimlessly
Contact damage
Delirium-Little-Horn
Little Horn
Summon dark balls, troll bombs
Create pits
Lil' Haunt Following in quick speed
Delirium-Loki
Loki
4 & 8-way blood-shots
Delirium-Lokii
Lokii
4 & 8-way blood-shots
Delirium-Mama-Gurdy
Mama Gurdy
Wave of blood-shots
Delirium-Mask-of-Infamy
Mask of Infamy
Mask: Ramming
Heart: 8-way blood-shots
Delirium-Matriarch
The Matriarch
Big blood-shot, leave red creep
Spawn Fistuloids, Fistulas
Delirium-Mega-Fatty
Mega Fatty
Wave of poop-shots
Spawn Dips
Leaping, may leave red creep
Delirium-Mega-Maw
Mega Maw
Ring of flames
Spawn Hoppers
Delirium-Mega-Satan
Mega Satan
Spawn Famine & Pestilence
Delirium-Mom
Mom
Stomp constantly
Delirium-Moms-Heart
Mom's Heart
Appear with Eyes
Wave of blood-shots
Delirium-Monstro
Monstro
Leaping
Spew amount of blood-shots
Delirium-Monstro-II
Monstro II
Leaping
Brimstone-beam
Spawn Suckers
Delirium-Mr-Fred
Mr. Fred
8-way blood-shots
4-way big blood-shots
Spawn Freds
Delirium-Peep
Peep
Leaping
Leave yellow creep
Ring of pee-shots
Peep Eyes
Delirium-Pestilence
Pestilence
Explosive shot, leave green creep
2nd Phase: Spawn Attack Flies
Delirium-Pin
Pin
Hide underground
Jump directly to the player
Explosive shot
Delirium-Polycephalus
Polycephalus
Hide underground
Blood-shots
Delirium-Rag-Man
Rag Man
Psychic blood-shots
Spawn Raglings
Rebirth pillars
Delirium-Rag-Mega
Rag Mega
Protected by purple balls
Spawn Raglings
Rebirth pillars
Delirium-Scolex
Scolex
Hide underground
Jump directly to the player
Spew amount of blood-shots
Explosive shot
Delirium-Sisters-Vis
Sisters Vis
Bouncing, leave green or brown creep
Brimstone-beam
Wave of blood-shots
Spawn Begottens
Delirium-Stain
The Stain
Hide underground
Wave of blood-shots
Spawn Round Worms
Delirium-Steven
Steven
Big: Follow
Small: Enraged quickly
Delirium-Teratoma
Teratoma
Division
Spawn Spiders
Delirium-Triachnid
Triachnid
Spawn Trites
Stomping, 8-way blood-shots
Delirium-Turdling
Turdling
Leave brown creep
Spawn Corns
Ramming
Delirium-Uriel
Uriel
Light beams
Blood-shots
Delirium-War
War
Summon troll bombs
Dash, leave troll bombs
2nd phase: Follow
Delirium-Widow
Widow
Jump
Spawn Spiders, Sacks
Leave white creep
Delirium-Wretched
The Wretched
Jump
Spawn Big Spiders, Trites
White blood-shots, leave white creep

Note Notes

  • If Delirium is killed in its Brownie form, it will spawn many Dank Squirts.

Question Trivia

  • So far, this is the only boss to have the most amount of health than any other previous bosses.
  • Delirium's boss transformations are chosen by previous bosses the character have fought in the run. This can be proven by running a mod, going into the console, beating 1 or 2 bosses, then summoning Delirium.
  • Delirium-Hush-2

    Unused form for Delirium, based on Hush's second form.

    Delirium has an unused form of Hush's second form, which can be found within the game's files.
  • Delirium's true appearance could slightly resemble Hush's unused skinless form.
  • The word "delirium" is a serious disturbance in mental abilities that results in confused thinking and reduced awareness of the person's environment.
    • Delirium's name may actually suggest by its shape-shifting ability.

Quarter Related Achievements

Afterbirth †

Bosses
The Binding of Isaac / Rebirth
Regular bosses Original: BlastocystChubDuke of FliesThe FallenFistulaGeminiGurdyLarry Jr.LokiMonstroPeepScolex
(Wrath of the Lamb: Daddy Long LegsGurdy Jr.Mask of InfamyPinWidow)

Rebirth: Dark OneDingleGurglingsThe HauntMama GurdyMega FattyMega MawMr. FredPolycephalus
(Afterbirth: BrownieDangleLittle HornRag ManTurdlings)
(Afterbirth †: Big HornRag Mega)

Posthumous Bosses Original: Monstro II
(Wrath of the Lamb: The Blighted OvumThe BloatCarrion QueenThe HollowThe HuskLokiiTeratomaThe Wretched)

Rebirth: The AdversaryThe CageThe Gate
(Afterbirth: The ForsakenThe FrailThe Stain)

Alternative Bosses Original: C.H.A.D.GishSteven
(Wrath of the Lamb: Triachnid)

Rebirth: Sisters Vis (Afterbirth †)

Harbingers Original: WarFamineDeathPestilenceHeadless Horseman

(Wrath of the Lamb: Conquest)

Final Bosses Original: It LivesMomMom's HeartSatan
(Wrath of the Lamb: ???Isaac)

Rebirth: The LambMega Satan
(Afterbirth: HushUltra Greed)
(Afterbirth †: Delirium)

Seven Deadly Sins EnvyGluttonyGreedLustPrideSlothWrath
Seven Super Deadly Sins Super EnvySuper GluttonySuper GreedSuper LustSuper PrideSuper SlothSuper WrathUltra Pride
Angels / Demons Original: Krampus

Rebirth: GabrielUrielFallen Angels

The Legend of Bum-bo
Regular bosses BygoneDuskGibsGizzardaLoafPeeperPyreSangreShy GalThe Duke
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