Key Piece 1

Key Piece 1 is an unlockable passive item.

Effect

 * Combined with, unlocks the golden gate in the starting room of The Chest and Dark Room to fight Mega Satan.
 * Increases the chance of finding an Angel Room.

Trivia

 * This item is used in Challenge #26 (I RULE!).
 * This item is used in Challenge #34 (Ultra Hard)