Has the same effect as the card or rune currently held by Isaac.
Damages all enemies in the room significantly.
If the box is empty, picks up all items and pickups in a room and stores them. If the box is not empty, places all stored items and pickups in the current room.
Breath of Life
Grants a brief moment of invincibility when the charge bar hits zero. If spacebar is held for an additional second after hitting zero, Isaac will take damage.
Throws out a blue flame that can pass over gaps (but not through rocks). The flame damages anything in its path.
Book of Shadows
Upon use, creates a protective shield nullifying all types of damage for 10 seconds.
Upon use, rerolls all passive items on Isaac like the D4, every pedestal item in the room like The D6, and every pickup like the D20.
Box of Friends
Upon use, duplicates all of Isaac's familiars for the current room.
When used, teleports Isaac to a random room that has not been explored yet. If all rooms are explored, including secret rooms, it will teleport Isaac to the Devil or Angel room. If all rooms are explored, including the Devil or Angel room, it will teleport Isaac to the I AM ERROR room. If used in a room with enemies, it will teleport Isaac out and back into the exact same room.
Rerolls the enemies in a room. Only rerolls enemies that are still alive (does not spawn new enemies).
Restarts the current room and brings back all enemies, allowing more rewards to be acquired by completing the room.
Throwing the ball at an enemy instantly kills it and captures it. The captured enemy can later be released and will be charmed until it dies, persisting between floors.
Dead Sea Scrolls
Triggers the effect of a random activated item from a list of possible options (not every activated item is included).
Forget Me Now
When activated, the level ends and is freshly regenerated with new rooms, monsters, and items. Disappears after use.
Shoots 10 tears in a circle around Isaac, which retain the damage, shot speed, and special effects (such as poison) of Isaac's tears.
Throws a persistent flame that deals high damage and diminishes as it damages enemies or blocks shots.
Book of Revelations
Adds 1 soul heart, increases the chance for a Devilor Angel Room to appear, and increases the chance for the next boss to be a Horseman (except on XL floors and floors with fixed bosses such as Mom).
Spawns a pile of poop where the character is standing and knocks nearby monsters back. May yield pickups like regular poop.
Head of Krampus
Fires a cross-patterned brimstone shot, just like The Fallen and Krampus shoot.