Mystery Sack

Mystery Sack is an unlockable passive item.

Effects

 * Spawns a familiar that drops a Heart, coin, bomb, or key (or any of their variations) alternatingly every 5 or 6 rooms.

Synergies

 * : The familiar drops pickups alternatingly every 4 or 5 rooms.

Trivia

 * Before patch 1.04, this item did not drop any items or do anything at all. Why it did not work remains a mystery.

Seeds
A3ES 1TQN (First floor, Treasure room next to spawn) QHKQ ZE4N (First floor, Treasure room next to spawn) CGVC XKY3 (Play as Isaac, and reroll the first item in the secret room just below the starting room) Q73A BMMP (adjacent to starting room) 3CAR V7Z0 (First Golden Treasure Room)