Satanic Bible

Not to be confused with The Book of Belial.

Satanic Bible is an unlockable activated item.

Effects

Gives one Black Heart.
Once used, the boss for the floor will drop a Devil Deal instead of a Boss Room item. This item must be paid for with hearts and will prevent Angel Rooms from generating under most circumstances if taken, just like a normal Devil Deal.
- This does not affect The Polaroid, The Negative, or Dad's Note.
This item belongs to the Bookworm set. Collecting three items from this set will transform Isaac into Bookworm.

Notes

If taking a Deal leaves Isaac with no health remaining, he can still survive by taking the Deal and then activating Satanic Bible, which will leave him at 1 black heart. This will only work if the Deal is a passive item, as trading Satanic Bible with an active item will make you unable to use it.
Bosses with set drops aside from Mom will still drop their normal item, but at the cost of one Heart Container.
On XL floors, both items will become Devil Deals, even if Satanic Bible was only used once.
The Lost, Tainted Lost, and Tainted Jacob in his ghost form can safely take any Boss Room item pedestals and it has no effect on subsequent devil deals.
- This also applies to the Lost form granted by the white fire on Downpour / Dross II. Taking a deal in this form will not remove hearts, making the player able to get at least 2 Devil Room items for free on that floor.
- This does not affect the items dropped on The Void.
Using the Satanic Bible changes the Boss Room's item pool to the Devil Room item pool for purposes other than direct boss rewards as well. This works even if the boss does not normally drop items, such as Mom, Satan, or ???.
- Rerolls such as The D6, Rune of Perthro, or Soul of Isaac will generate Devil Room items.
- Using Satanic Bible after the Boss Room item has spawned, followed by any reroll, causes the new item to be drawn from the Devil Room item pool, but it will have no heart cost. Taking this item will not prevent Angel Rooms from spawning.
In True Co-op, the pedestal's additional items will also be Devil deals, but be drawn from the Boss item pool.
Using Satanic Bible on Downpour / Dross II will affect the Mirrored World Boss drop.

Synergies

Book of Virtues: Spawns black wisps in the middle ring, looking like a red inverted cross. Each wisp increases the chances of Devil Room appearing by 10%.
Converter: Allows for generation of Heart Containers. (Schoolbag required)
Car Battery: Gives Isaac two black hearts.
Soul of the Lost: The Devil Deal can be taken for free.
There's Options: 2 Devil Deals will be offered, but only one can be taken.
Coupon: The Devil Deal can be taken for free. Schoolbag is recommended.
Dream Catcher: If the floor boss is revealed to be one of the horsemen, and the player has no interest in the Cube of Meat, or doesn't mind paying health for it, Satanic Bible can be used early.

Interactions

Book of Revelations: The spawned Ball of Bandages or Cube of Meat will cost hearts like a normal devil deal.
Chaos: The item spawned will be chosen from a random item pool instead.
Genesis: The boss item is still a devil deal even after using Genesis.
Lemegeton: Will generate wisps from the Devil Room item pool when used inside the Boss Room after Satanic Bible is used.
Redemption: Taking the boss's item when it's affected by Satanic Bible will remove the cross however the Boss Room can't give the cross.
Vanishing Twin: The second boss spawned will also drop an item from the Devil Room item pool that must be paid for.
Vanishing Twin + Ascent: After using Satanic Bible If an Item spawned by Vanishing Twin is not bought with hearts it can be bought with coins during the Ascent.