A piece of paper with text on it, and blood dripping off the lower right edge.
Turns Isaac's body black, gives him small horns, and makes him seem more aggressive.
Increases Damage by 1 and tears by 2, 4 or 5 (depending on your current tear fire rate and items in possession). The player also gains 2 Soul Hearts.
- The Icon is presumably a contract between Isaac and Satan, as the item turns you into a little demon, whereas Lord of the Pit only gives demonic appearance.
- The Pact seems to be signed in blood. In satanic rituals a contract with a demon is usually signed with its conjurer's blood. See also Wikipedia on Pacts with the Devil.
- When playing as ??? (The Blue Baby), if you have three Soul Hearts or less and take The Pact, you will still have two soul hearts remaining, but you will lose the game.