Crystal Key

Effects

• Whenever Isaac clears a room, has a chance to open a neighboring (Red Room) Red Room.
  • This effect can occur while Isaac is inside a Red Room, but the chance is smaller.

Notes

• It's possible to increase the chance of a (Red Room) Red Room unlocking if multiple Crystal Keys are held, e.g. from absorbing using (Smelter) Smelter, holding (Mom's Box) Mom's Box, having a golden Crystal Key, or other methods. The chance for a Red Room door to unlock depends on the number of Crystal Keys held and if the room cleared is normal or Red.

| Crystal Key Count | Normal Room | Red room | | --- | --- | --- | | 1 | 33.3% | 12.5% | | 2 | 50% | 16.6% | | 3 | 100% | 25% | | 4 | 100% | 50% | | 5 | 100% | 100% |

• Each cleared wave of a (Challenge Room) Challenge Room has a chance to generate an adjacent Red Room.
• Rooms that are re-fought using the (D7) D7 have a chance to generate additional Red Rooms.
• Doors do not have to open to an actual valid Red Room, and can lead outside the map and into an (I AM ERROR) I AM ERROR Room.