Key Bum

Key Bum is an unlockable passive item added in Afterbirth.

Effects

 * Spawns a familiar that follows Isaac around and collects keys, dropping random Chests in return. (He does not fill up a familiar "slot".)

Synergies

 * : Familiar is bigger and drops chests more often.
 * The Left Hand/Gilded Key: Works as expected.
 * Flat Penny: Chests frequently contains pennies, which have a chance of spawning more keys for Key Bum to pick up, possibly lead to a loop.
 * Allows Isaac to choose which Locked Chests are worth opening and which to pass, thus saving keys. Great for min-maxing.

Seeds
WJK1 9R0Z (Treasure Room adjacent to spawn)