The Polaroid

The Polaroid is an unlockable passive item.

Effects[]

If the character has half a red heart or no red hearts after taking damage, it triggers the Book of Shadows effect, creating a shield that nullifies all types of damage for 5 seconds.
Allows entrance into Chest after beating Isaac in the Cathedral by touching the chest.
Opens A Strange Door in Depths II and its variants that leads to Mausoleum/ Gehenna II.
- Unlike with the Chest entrance, The Polaroid gets consumed by the door and vanishes from Isaac's inventory.

This item is a guaranteed drop from Mom alongside the The Negative, provided they are unlocked. However, they are mutually exclusive: Once one of them is picked up, the other one will disappear.
- With the use of either a teleportation item and 5 pip Dice Room, a Forget Me Now, or R Key, both the Polaroid and the Negative or multiple copies of the Polaroid or Negative can be obtained.
The Polaroid always triggers when taking damage as characters who lack Red Heart containers, such as Azazel and Tainted Azazel (by default), ??? and Tainted ??? (permanently), Dark Judas and Tainted Judas (permanently), The Forgotten (only as the soul), Tainted Forgotten (permanently), Dead Tainted Lazarus (by default), Tainted Bethany (permanently) or any other character who has chosen to trade away their heart containers in deals with the Devil, Black Markets, or with Guppy's Paw or the Potato Peeler. It will also trigger if the character has only half of a red heart left.
The Polaroid will be the leftmost item after defeating Mom, in case Curse of the Blind is active.
It is possible to obtain two Polaroids by obtaining one as an Eden starting item.
Obtaining multiple copies of The Polaroid does not cause its effect to stack.
As with all items crucial to story progress ( Key Piece 1 and Key Piece 2, Knife Piece 1 and Knife Piece 2, Dad's Note, and Dogma), this item has protection from full-run rerolls. It does not, however, share the immunity Dad's Note has to D6-type rerolls and Void.

In the original Binding of Isaac flash game, The Polaroid used to be a trinket that Mom would drop in addition to a regular collectible from the boss pool. When it was originally implemented, it was only available in the normal Trinket drop pool and was implemented secretively. Players were frustrated, so, with an update, Edmund made it so it would also only drop if the player took no red heart damage against Mom, similar to the conditions for the Devil Room to open its path. Since players would not always receive the Polaroid and might switch it out with another trinket, Edmund wanted to make the discovery of Chest (and its at-the-time new ending) something special.
As soon as The Polaroid or The Negative become available, they will drop in place of the regular Boss Room item Mom would otherwise provide, essentially providing a difficulty increase for Womb and beyond after either has been unlocked.
- They can, however, be re-rolled (or converted into stat increases with Void) at the cost of closing off access to Chapter 6.

PC NTKG 9MMP (Starting item for Eden)