Delirious

Delirious is an unlockable activated item added in The Binding of Isaac: Afterbirth †.

Effect

Upon use, spawns Delirium in a form of a friendly boss.
- The boss lasts for the current room, or until killed.
- The boss persists between rooms until killed. Using the item again will kill the current summoned boss if it is still alive. Any friendly monsters spawned by the previous boss will also be killed.
  - If used on a boss that has a phase change which requires the boss to die, the boss will still persist in its new phase (i.e. The Frail or Fistula). (This may be a bug as some bosses, such as Blastocyst, are unaffected)
Charge time varies depending on the strength of the previously summoned boss.
Changes the appearance of the current room so it looks like a different chapter.

Boss List

Charges	Boss
6 rooms	Gemini, Dingle, Gurglings, Larry Jr., The Duke of Flies, Widow, Pin, Dangle, Turdlings, Famine, Gurdy Jr., The Husk, The Hollow, Loki
8 rooms	Monstro, Steven, Blighted Ovum, The Haunt, Little Horn, Rag Man, Fistula, Chub, C.H.A.D., Gurdy, Mega Fatty, Mega Maw, Peep, Dark One, Polycephalus, The Wretched, The Forsaken, The Frail, Rag Mega, Pestilence, Gish, Brownie, War, Blastocyst, Scolex, Mr. Fred, Lokii, Daddy Long Legs, Triachnid, Teratoma, Death, Headless Horseman (body)
12 rooms	Carrion Queen, The Stain, Big Horn, Monstro II, The Cage, The Gate, The Adversary, The Bloat, Mask of Infamy, Sisters Vis, Conquest, The Fallen, Hush

If a boss does not appear on this list, it cannot be spawned.

Hush has an extremely low chance of spawning.
Sometimes bosses don't spawn because of grid entities getting in the way. When this happens, the upper door appears to have friendly particles.
Unlike Mega Blast, this item can be charged with a single Lil' Battery.
- Lil' Battery gives 6 charges.
Delirious has a 60% decreased item pool weight, making it less likely to appear than other collectibles.
Using Delirious in the Delirium fight is ill-advised, as it can be confusing which Delirium is the right one to attack.
Some bosses leave fires on the ground, such as the orange champion Little Horn, which can still hurt Isaac.

Book of Virtues: Generates a white wisp that resembles one random boss from this list:
- Monstro: Fires an inaccurate spray of 6-10 tears, similar to Lil Monstro but without the charge time.
- The Duke of Flies: Creates Blue Flies instead of firing tears. Each wisp can have a maximum of 3 flies at a time.
- Loki: Fires four tears that alternate between cardinal and ordinal directions.
- The Haunt: Fires Brimstone lasers. The laser does not need to be charged to be fired, and can tick up to 8 times for a total of 8 damage.

Blood Puppy: Either angry version of Blood Puppy will target friendly bosses as well and can drag them along with it when it charges them. Blood Puppy cannot damage friendly bosses; however, friendly bosses can damage Blood Puppy despite not targeting it outright.
Broken Modem: Broken Modem also affects friendly bosses and projectiles created by them.
Eraser: The thrown Eraser can’t hit friendly bosses; however, if it erases their hostile variant, they too are erased. If Delirious attempts to spawn an erased boss, it will fail to do so, wasting a use.
Ghost Bombs / Hungry Soul / Purgatory / Vade Retro: Explosions from ghosts can harm friendly bosses.
Tick: Friendly bosses start with less health if they have over 60HP.

This item was most likely intended to be the "ultimate item" of Afterbirth †, similar to Mega Blast of the Afterbirth DLC.

Bug!	If Delirious is used during the Delirium fight and the charmed boss is killed, it will act as if Delirium was killed, but no chest will spawn.

Bug!	If a Pink Champion Polycephalus is spawned by the item, one will have the Delirium skin and the other will have the normal Polycephalus skin.

Bug!	If Lokii is spawned by the item, one will have the Delirium skin and the other will have the normal Lokii skin.

Bug!	If a Pink Champion The Cage is spawned by the item, one will have the Delirium skin and the other will have the normal The Cage skin.

Bug!	Using Delirious multiple times rapidly in the same room can crash the game.

Bug!	Using Delirious in Boss Rush or Boss Challenge Room can close the exit even if it was finished beforehand, likely softlocking the player.

Bug!	Using Delirious can sometimes spawn a boss without its Delirium skin.

Bug!	If Delirious is used against Loki in a room layout where a Poky is present, the Poky will not deactivate until the boss and any enemies it spawns die (which may take an extremely long time). If the player has no card, pill, or rune to teleport them out of the room, this is effectively a softlock.

Bug!	Using Delirious during Mega Satan or Beast fight can lead to a softlock.

Bug!	If a Mega Fatty is spawned by the item during The Beast fight, when the Mega Fatty inhales, it will move the sprites of the bosses in the background.

Bug!	If Delirious summons Rag Mega in an uncleared room, the Purple Balls will prevent the room from clearing, effectively causing a lengthy softlock - The friendly Rag Mega does steadily lose health on his own, but this takes a fair while.