Dark Bum

Spawns a familiar that follows Isaac around and collects Red Hearts for himself. For every 1½ Red Hearts collected, Dark Bum will give a Soul Heart, a hostile Spider, a friendly Blue Spider, or a random card, rune or pill.

"He wants to take your life"

• Spawns a familiar that follows Isaac around and collects Red Hearts. (He does not fill up a familiar "slot".) For every one-and-a-half Red Hearts collected, Dark Bum will generate one of the following:
  • A hostile Spider.
  • A friendly Blue Spider.
  • A single Black Heart.
  • A random pill, card or rune.

• 
  Little C.H.A.D. - Each Half Red Heart dropped by Little C.H.A.D. can be collected by Dark Bum, increasing the amount of pickups dropped.

• Baby Shop
• Devil Beggar
• Devil Room
• Treasure Room