Using Delirious can sometimes spawn a boss without its Delirium skin. Using Delirious in Boss Rush or Boss Challenge Room can close the exit even if it was finished beforehand, likely softlocking the player. Using Delirious multiple times rapidly in the same room can crash the game. 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. If Lokii is spawned by the item, one will have the Delirium skin and the other will have the normal Lokii skin. 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. 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. Mega Mush and Death Certificate are similar in unlocking complexity in the Repentance DLC.This item was most likely intended to be the "ultimate item" of Afterbirth †, similar to Mega Blast of the Afterbirth DLC.Tick: Friendly bosses start with less health if they have over 60HP.Ghost Bombs / Hungry Soul / Purgatory / Vade Retro: Explosions from ghosts can harm friendly bosses.If Delirious attempts to spawn an erased boss, it will fail to do so, wasting a use. Eraser: The thrown Eraser can’t hit friendly bosses however, if it erases their hostile variant, they too are erased.Broken Modem: Broken Modem also affects friendly bosses and projectiles created by them.Blood Puppy cannot damage friendly bosses however, friendly bosses can damage Blood Puppy despite not targeting it outright. 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.The laser does not need to be charged to be fired, and can tick up to 8 times for a total of 8 damage. Loki: The direction the tears are fired alternates between the cardinal and ordinal directions, similar to Loki's Horns.The Duke of Flies: Each wisp will create and can have up to 3 Blue Flies out at a time, similar to Rotten Baby.Monstro: Fires an inaccurate spray of 6-10 tears at a time, similarly to Monstro's Lung but without the charge time.
It is possible for Hush to spawn, despite Delirium not transforming into Hush during its boss battle.Unlike Mega Blast, this item can be charged with a single Lil' Battery.When this happens, the upper door appears to have friendly particles. Sometimes bosses don't spawn because of grid entities getting in the way.Changes the appearance of the current room so it looks like a different chapter.Upon use, spawns Delirium in a form of a friendly boss for the current room.