Key Bum is an unlockable familiar in The Binding of Isaac, added in the Afterbirth DLC.

Spawns a familiar that follows Isaac and collects keys. It has a 20% chance of dropping a random chest upon collecting a key.

Picking up a Charged Key will make Key Bum spawn a Lil' Battery.

Key Bum cannot pick up Golden Keys.

This page shows information as of the latest Repentance release.
To see latest up-to date information about this item for the new Repentance+ (Online Co-op) DLC, check this page instead.

Defeat Ultra Greed as Lazarus.

This item contributes towards the Super Bum transformation. Collecting 3 items from this set will transform Isaac's bums into Super Bum, a familiar that collects coins, red hearts and keys, and drops twice as many rewards.

Key Bum can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for Key Bum have been documented.

* Note that not all possible synergies and interactions are listed here.

• Check out the item description on the external Isaac Wiki.