Abaddon 
Effects
- +1.5 damage.
- +0.2 speed
- (Removed in Repentance) Also affects maximum speed (may never exceed 2.0).
- (Removed in Repentance) Removes all Red Heart containers and grants 6 (Black Heart) Black Hearts.
- (Added in Repentance) Converts all Red Heart containers into Black Hearts, and adds 2 additional Black Hearts.
- (Added in Afterbirth †) Will not remove (Added in Afterbirth †) (Bone Heart) Bone Hearts, but will empty them.
- Adds a chance to shoot fear tears.
- (Added in Afterbirth) This item belongs to the Leviathan set. Collecting three items from this set will transform Isaac into Leviathan.
Notes
- The fear effect chance depends on the Luck stat, starting at 12.5% at 0 Luck, reaching 100% with 85 Luck.
Dark Matter is significantly better at inflicting fear than Abaddon.
- Does not remove (Soul Heart) Soul Hearts or (Eternal Heart) Eternal Hearts.
- (Removed in Repentance) As it removes all Red Heart Containers, other Deals with the Devil can be taken for "free" as long as Abaddon is taken last while still having at least 1 Container.
- (Removed in Repentance) Has no negative trade-off when taken as (???) ???, minus losing the opportunity of an (Angel Room) Angel Room.
- Can always be taken when offered as a 3 Soul Heart Deal. Even if Isaac only has one or two Soul Hearts, the Black Hearts will be granted after taking the item.
- (Added in Afterbirth † / Removed in Repentance) Will instantly kill the (Keeper) Keeper when picked up.
- (Added in Repentance) (Bethany) Bethany will be left with half a Red Heart with her other Heart Containers removed.
- (Added in Repentance) (Tainted Bethany) Tainted Bethany will not lose stored Red Hearts, but can't gain more black hearts from this item as a result.
Synergies