Blanket

Blanket is an unlockable passive item added in The Binding of Isaac: Afterbirth † (Booster Pack #5).

Effects

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

This item's shield effect has the same synergies and interactions as Holy Mantle with the only difference being that when paired with Holy Mantle or The Lost's innate shield it can still reapply later into the run. For a list of synergies and interactions, visit that page.
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 which occasionally contains a bed.

Blanket is based on this Steam Workshop item by P.5000 and Ratlah, originally known as Security Blanket.
This item is part of a set of bedtime-themed items, including Binky, Mr. Dolly, Night Light, and PJs.
This item may be a reference to Linus van Pelt's famous blue security blanket, as seen in Peanuts.