- For other uses, see Keeper (disambiguation).
It is unlocked after beating Ultra Greed as Lazarus.
- Spawns a familiar that follows Isaac around and picks up keys for himself. He will drop random Chests in return.
- The trinket Flat Penny has a chance to spawn a key upon collecting a coin. This will allow key bum to collect more keys and give you more chest.
- It is one of the items for the Super Bum transformation.
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