Book of Revelations

**Book of Revelations** is an unlockable activated item.

## Effects

* On use, gives one Soul Heart.
* Increases chance for a Devil Room or Angel Room door to open if held while killing the final boss of the floor.
	+ The chance is increased by 35%.
	+ The chance is increased by 17.5%.
* If the Book of Revelations is used at least once on a floor, a Harbinger will replace the current floor's boss if possible.
	+ This will always happen as long as the floor's respective Harbinger has not been encountered, the boss has not been fought yet, and a Harbinger can appear on the floor normally.
	+ This has a high chance to happen but is not guaranteed.
* This item belongs to the  set. Collecting three items from this set will transform Isaac into Bookworm.

## Notes

The Harbingers capable of appearing, and the floors they appear on, are as follows:

1. Famine in Chapter 1
2. Pestilence in Chapter 2
3. War in Chapter 3, floor 1
4. Death or Conquest (if unlocked) in Chapter 4, floor 1
5. The Headless Horseman on any floor in Chapters 1-4

* Set bosses ( Mom, Isaac, The Lamb, etc.) are unaffected by Book of Revelations.
* Only the first boss of a floor affected by Curse of the Labyrinth is affected.
* Book of Revelations won't replace the boss on double-sized Boss Rooms, like Double Trouble rooms or if the boss is Mr. Fred.
	+ Furthermore, if the Book of Revelations is used on the first floor of a Chapter with a Double Trouble room no Harbinger will spawn on the second floor, even if Book of Revelations is used again. If finding a Harbinger is desired, Isaac should wait until seeing the shape of the Boss Room before using it.
* Keeping Book of Revelations until Chapter 4 is one of the methods to unlock achievements related to Super Meat Boy and Super Bandage Girl, explained in detail here.
* This item can replace the Boss even after Isaac initiates a battle with a normal boss and then teleports out before the fight is completed.
* This item can replace The Bloat with a Harbinger in Aprils Fool (challenge #32).
* Bosses in Downpour / Mines / Mausoleum and their variants cannot be replaced with Harbingers.

## Synergies

* : Creates wisps in the inner ring, resembling tiny crosses that do not fire tears. The wisps create a Harbinger that spawns Locusts (the same ones that  creates) for the current room when destroyed.
* : Gives Isaac two soul hearts.
* : Defeating a Boss after using the book at least once in the floor will spawn both a regular Boss pool item and either  or .

## Interactions

* : Effects on the Boss Room and boss item still apply to the floor even after using Genesis.
* : The spawned  or  will cost hearts like a normal devil deal.

## Trivia

* *The Book of Revelation* (note the lack of an "s") is the final book of *The Bible*. It depicts the apocalypse through a vision shown to John of Patmos and includes the Four Horsemen and themes of Hell, Satan, and The Lamb. This explains why using it causes the next boss to be a Harbinger, as well as why it increases the chances of a Devil Room / Angel Room to appear.

## Gallery

* 3DS The icon of Book Of Revelations as seen on the lower 3DS screen.
* Book of Revelations's splash image which appears when it's activated.