Binding of Isaac: Rebirth Wiki
Binding of Isaac: Rebirth Wiki

Disambig.png This article is about the boss at the end of The Chest. For the character, see ??? (Character). For other uses, see ??? (Disambiguation).

??? is the boss of Chest Chest, accessed by defeating Isaac in the Cathedral Cathedral while holding 15►The Polaroid The Polaroid, which is always dropped by Mom after defeating Isaac five times. He is a posthumous version of Isaac, and the final boss of Ending 14.


??? lies on the ground in the middle of the room and does not begin attacking until he takes damage.
During all three of ???'s phases, he continuously shoots multiple projectiles in the Isaac's direction at fixed intervals when not performing other attacks at a faster rate than Isaac. After taking enough damage, he begins to shoot double and triple projectiles.

  • Each projectile has a chance of having a homing effect.

Phase 1[]

??? remains stationary on the ground and performs the following attacks:

  • Shoots 7-8 rapid-fire lines of projectiles in all directions that expand outwards. After taking enough damage, these lines curve while travelling.
  • Shoots 8 lines of 2 projectiles in all directions that expand outwards. Each line consists of one normal projectile and one homing projectile. After taking enough damage, these lines curve while travelling.
  • After taking enough damage, ??? summons Attack Flies, Moters, or Pooters that orbit around himself.
    • Pooters have a farther orbit than the other flies.
    • Attack Flies spawned from Moters chase Isaac instead of orbiting ???.

Phase 2[]

2 Eternal Flies that can block tears begin to circle ???, who stands up but remains stationary and performs the following attacks:

  • Continues to spawn orbiting flies.
  • Fires 4 homing projectiles in a lop-sided X pattern.
  • Fires 8 homing projectiles in all directions.

Phase 3[]

??? grows a pair of angelic wings and is no longer stationary, slowing drifting towards Isaac and performing the following attacks:

  • Spawns orbiting flies more frequently.
  • Teleports to a position in front of Isaac- predicting his movements and attempting to cut him off. Teleports directly on top of Isaac if he isn't moving.
  • Performs the 2 projectile patterns from the first phase.


Unlockable Achievements[]


  •  ??? cannot teleport during his third phase if he is slowed (e.g. using 15►Stop Watch Stop Watch).


  •  ??? was added in the Wrath of the Lamb DLC for the original The Binding of Isaac.
  • The music that plays during this boss fight is titled Ascension.[1] The term "ascend" is typically used in religion as the act of one's soul rising to Heaven.
  •  ???, along with Isaac, teleport away upon defeat and do not "die".
  •  ??? is commonly referred to as the 'blue baby' by the Binding of Isaac community, as well as Steam Achievements.
  • Added in Afterbirth ??? is fought as the first phase of Hush with identical behavior and music, only using a different sprite. The Hush version also has half the HP.
  • Added in Afterbirth † Delirium's ??? form is one of its only forms that don't have any melted features, along with both of the Angels.
  • This is the posthumous version of Isaac (Boss)
  • Added in Repentance Blighted Ovum, Big Horn, Triachnid, and ??? are the only bosses whose portraits were completely changed in Repentance (beyond simply adding more detail). Of these, only Triachnid, Isaac, and ??? didn't receive new sprites.