Binding of Isaac: Rebirth Wiki

Added in Repentance
Disambig.png This article is about the trinket that creates Blue Womb rooms. For the trinket that opens the Hush fight and empowers Pandora's Box, see Strange Key.

Blue Key is an unlockable trinket added in The Binding of Isaac: Repentance.


  • Entering a room that requires a Key Key does not consume a key, but brings Isaac to a room resembling ??? ???, which acts as an in-between of the two rooms.
    • These rooms contain assortments of Blue Gaper Blue Gapers, Blue Boil Blue Boils, and/or Blue Conjoined Fatty Blue Conjoined Fatties, and are always long rooms (either normal or slim). They have a chance to give a reward when cleared, like normal rooms.
    • Once exited, the room cannot be re-entered.


  • Doors that were unlocked with the trinket have a blue hue emitting from them instead of the normal floor-dependent hue.
  • The doors leading to the entrance of Downpour Downpour or Dross Dross can be unlocked for free by Blue Key, though the blue room generated will be a dead end. Leaving the way Isaac came in will leave the door unlocked, allowing the player to continue normally.
  • Rooms that require money to enter (Arcade Arcades or rooms affected by Pay to Play Pay to Play) can also be opened for free.
  • Doors that require two keys to open, such as Vault Vaults or Dice Room Dice Rooms, will be opened instantly instead of waiting for the animation of both keys to be used.
  • The door leading to Hush Hush will also produce a blue room, despite not requiring a key.


  • Door Stop Door Stop / Mercurius Mercurius: The blue room can be exited without fighting the enemies, and the door will remain unlocked.

In-game Footage[]


  • The trinket is most likely a reference to SCP-860, a fictional key that acts in a near-identical manner.
  • If used on the ??? ??? floor, one might hear the mid-combat layer of the floor's theme, Nativitate, an asset which was previously unused.


Bug Bug! If used with The Forgotten and Birthright, leaving The Forgotten's body in the hallway will cause it to reappear next to you when you exit, but upon switching back to the body, it will become immobile, and switching back to the soul will make it immobile too, causing a softlock requiring you to exit then continue the run.
Bug Bug! Opening a locked door without entering it and then leaving and re-entering the room will no longer cause the door opened by Blue Key to lead to a Blue Womb room. In other words, this removes the downside of the trinket.