According to the Binding of Isaac Rebirth wiki:

If The Book of Revelations is used at least once in a map, a Harbinger will replace the normal level boss.

I've found Book of Revelations in a Library Room in Basement 1 after defeating Pin boss. So I moved to Basement 2 in order to activate the book and make my next boss Famine. In theory.

The fact is that I found Larry as Basement 2 boss. How is this possible? I mean, the book should replace my next boss with a Harbinger. Why not this time?

Meat Boy and Bandage Girl achievements are driving me nuts...

  • 1
    Are you sure it was the Book of Revelations? A couple of books have a similar appearance. Feb 7, 2015 at 7:13
  • 1
    Yes, I'm not dumb... It gave me a Soul Heart each activation.
    – pinckerman
    Feb 7, 2015 at 12:01
  • A soul heart or a black heart?
    – Arperum
    Feb 7, 2015 at 12:56
  • Soul, I know the difference between Book of Revelations and Satanic Bible.
    – pinckerman
    Feb 7, 2015 at 16:38

1 Answer 1


I've heard somewhere that the Horsemen can only spawn on the first floors. Basement/Cellar I, Caves/Catacombs I, Depths/Necropolis I, etc. But I can't find reliable information online to support this.

Also, this might also be why - According to platinumgod.co.uk,

Using this item gives you a higher chance of finding a horsemen boss at the end of the floor.

This might mean that the Book of Revelations only gives you a higher chance (although a very high one at that) of spawning a Horseman for the boss.

And if you're looking to get the Meat Boy/Bandage Girl achievements, save yourself the pain of Conquest ruining your day and go for the Monster Manual + infinite item charge approach.

  • I've heard that, too. But that's not true, because I've found Pestilence in Catacombs II recently using Book of Revelations. Anyway you may be right, I've always thought that would be a 100% chance. Rebirth wikia doesn't give exact information.
    – pinckerman
    Feb 25, 2015 at 23:37
  • Oh, and I've already got those achievements using Monster Manual abuse, that was the easiest way indeed.
    – pinckerman
    Feb 25, 2015 at 23:39

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