A gray book with an inverted pentagram on its cover.
Increases the chance of a Devil Room spawning by 25%.
- Judas starts the game with this item.
- As with most Activated Items, items such as Habit, 9 Volt and The Battery decrease the charge time, increasing the effectiveness of this item.
- This item's effect works with tear-changing effects such as Mutant Spider, The Inner Eye, Technology, Technology 2, Mom's Knife and Brimstone.
- Blood Of The Martyr - Damage is multiplied by 1.5 in addition to the normal +2 if Isaac possesses this item without also having Max's Head or Magic Mushroom.
- In the Dead Sea Scrolls, (not to be confused with the item of the same name) Belial is the leader of the Sons of Darkness.
- During development, there was an item known as Satanic Bible. It later evolved into the Book Of Belial.
- The Book of Belial is the third book of The Satanic Bible, and describes magic rituals.
- XV The Devil shares its effect with this item and does not stack with the Book of Belial.
- The upside down pentagram on the book is a widely known satanic ritual symbol.