Book of the Dead

Effects

When used, spawns one of the following for each enemy already killed in the current room:
- An orbital bone familiar (very common).
- A friendly (Bony) Bony (uncommon).
- (Added in Repentance) A friendly (Bone Fly) Bone Fly (uncommon).
- A friendly (Black Bony) Black Bony (rare).
- (Added in Repentance) A friendly (Revenant) Revenant (rare).
  - The chance to spawn Revenants is greatly increased in (Mausoleum) Mausoleum / (Gehenna) Gehenna / (Sheol) Sheol / (Dark Room) Dark Room.
This item belongs to the Bookworm set. Collecting three items from this set will transform Isaac into Bookworm.

Orbital bones deal contact damage equal to Isaac's damage at the time it was spawned and repel enemies that touch them.
- (Removed in Repentance) They block 3 shots or deal 2 ticks of contact damage before being destroyed.
(Removed in Repentance) Bonies deal 8.3 contact damage and 5 damage with thrown bones.
- (Added in Repentance) Bonies deal 8.7 contact damage and 6 damage with thrown bones.
Black Bonies will explode on death, dealing 40 damage to enemies it hits. The explosion will not hurt Isaac, (Removed in Repentance) but will knock him back.
Internally, the Book tracks each position an enemy was killed at in the current room, and uses those locations as spawn points for bone orbitals and Bonies; using the book gives a high probability for each location to give one of them.
- If one of these locations doesn't give a bone orbital or bony, it can still give one if the book is used in the same room without leaving. However, once a location gives something, it cannot do so again.
Using the book in a room that had no enemies or was re-entered does nothing and expends the charge.
Orbital bones occupy the same area around Isaac as Blue Flies, meaning Isaac can have an incredibly dense ring of bone orbitals around him that nullifies most attacks.
Friendly monsters killed in the current room can also be used by Book of the Dead.
Destroying (Black Poop) Black Poop will damage the friendly Bonies acquired from this item.

(Added in Repentance) Book of Virtues: Spawns tiny skull wisps on the inner ring. The wisps fire bones and spawn friendly Bonies when destroyed. The book will summon wisps regardless of whether or not there were enemies killed in the current room, and the ring of wisps is close enough to Isaac to be inside the ring of bone orbitals Book of the Dead makes.

(Baby-Bender) Baby-Bender: No effect.
Car Battery: Since dead enemies can be animated only once, Car Battery does nothing.
(Removed in Repentance) Contagion: Poison effect can spread to and kill friendly Bonies.
(Added in Repentance) Eraser: Bonies erased via Eraser will never spawn again from Book of the Dead, greatly decreasing its power.
(Added in Repentance) Ghost Bombs / Purgatory: Explosions from ghosts can and will kill Bonies.