Binding of Isaac: Rebirth Wiki

Rotten Baby is a passive item.


  • Spawns a familiar which spawns friendly Blue Flies when Isaac holds down a fire key.
  • Added in Afterbirth This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.


  • Spawns one Fly at a time.
  • Blue Flies deal 2x Isaac's damage.
  • Flies will be generated regardless Isaac's ability to fire tears normally.


  • Added in Afterbirth †Fish Tail Fish Tail: Rotten Baby will spawn two flies at a time.
  • Mongo Baby Mongo Baby: Mongo Baby will also spawn flies.


  • BFFS! BFFS!: Rotten Baby becomes larger, but this is only a cosmetic change.
  • Hive Mind Hive Mind: Fly damage is doubled.
  • Added in RepentanceThe Twins The Twins: Unlimited flies can be slowly generated by walking back and forth between rooms while firing. A new fly will generate each time Rotten Baby is duplicated.

In-game Footage[]


  • This item is used in The Family Man (challenge #19).
  • Even though the right side of Rotten Baby's face is decayed, when his sprite faces left, his left side appears decayed as well.


PC RXTX MGYV (Treasure Room adjacent to spawn)

PC Q9EQ XVQE (Treasure Room adjacent to spawn)

PC RDAM YDAV (Treasure Room adjacent to spawn)

PC Added in Afterbirth / Removed in Afterbirth † EBH3 A1PM (First floor treasure room)

PC Added in Afterbirth † Normal and hard modes only CGRP WYLB (Treasure Room adjacent to spawn)

PS4 RMJ8 JHGG (Treasure Room adjacent to spawn)


Bug Bug! PC Rotten Baby will be able to spawn more than one friendly fly if the run is left and then resumed.