Key Bum - The Binding of Isaac

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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 the latest information as of the new Repentance+ (Online Co-op) DLC.
To see information about this item for the previous Repentance version, 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:

Name	Weight
Treasure Room	1.0/1.0
Secret Room	1.0/1.0
Key Master	1.0/1.0
Baby Shop	1.0/1.0

The following tags are applied to this item:

Id	Description
summonable	Can be summoned via Lemegeton.
offensive	Can appear for Tainted Lost.

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

Mod	Item	Synergy
---	BFFS!	Increases the chance of dropping chests.

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

Below is the Internal Item Description as shown in-game.
Note that some stat changes are not displayed here. Please see the main description for the full effects.

Key Bum

• Wandering familiar that consumes key pickups from the ground and spawns random chests in return
• Abyss: x1 hungry locust .5x Isaac's damage