Binding of Isaac: Rebirth Wiki

Added in Afterbirth

Key Bum is an unlockable passive item added in The Binding of Isaac: Afterbirth.


  • Spawns a familiar that follows Isaac around and collects keys, dropping random Chests in return. (He does not fill up a familiar "slot".)
  • This item belongs to the Super Bum set. Collecting three items from this set will transform Isaac's bums into Super Bum.



  • BFFS! BFFS!: Familiar is bigger and drops chests more often.
  • Flat Penny Flat Penny: Chests frequently contain pennies, which have a chance of spawning more keys for Key Bum to pick up, possibly lead to a loop.
  • Added in RepentanceGilded Key Gilded Key / The Left Hand The Left Hand: Works as expected.
  • Added in RepentanceGuppy's Eye Guppy's Eye: Allows Isaac to choose which Locked Chests are worth opening and which to pass, thus saving keys. Great for min-maxing.

In-game Footage[]



PC WJK1 9R0Z (Treasure Room adjacent to spawn)


Bug Bug! If Credit Card Credit Card is used in a Shop Shop with Keys, Key Bum will not be able to pick up the free keys. This can be fixed if Isaac leaves and re-enters the shop.
Bug Bug! Added in Afterbirth † / Removed in Repentance Charged Key Charged Keys do not increment Key Bum's key count when picked up.