Blanket

Effects

Heals one (Red Heart) Red Heart.
Grants one (Soul Heart) Soul Heart.
Upon entering a (Boss Room) Boss Room, grants a shield that blocks one hit, then disappears.

If the shield is not broken before leaving the room or entering the next floor, it will disappear by itself.
Reentering a boss room after the boss has been defeated will still grant a shield.
Multiple Blankets will only give 1 shield.
In Greed Mode, this item grants a shield only for the two boss fights on the final level. The shield does not activate for the regular boss waves on previous floors.
To quickly unlock this item, keep restarting Greed mode to enter its (Curse Room) Curse Room which occasionally contains a bed.

Holy Mantle: The effect stacks, granting two shields in Boss Rooms.
(Removed in Repentance) Stop Watch: Blocking damage with the shield will activate Stop Watch's effect.
(Holy Card) Holy Card: The effect stacks, granting two shields in Boss Rooms. However, the Holy Card effect works first and you will lose it even if you took only one hit.