Gives one Soul Heart, +0.7 damage, -0.18 speed, and the ability to destroy most obstacles by walking into them. Cannot be stacked in one room.
Isaac deals 40 contact damage to enemies, once per second. Does not prevent Isaac from taking contact damage.
Gives half a Black Heart, +2 damage, -0.18 speed and the ability to destroy obstacles for the current room.
If used multiple times in one room, the speed penalty only applies once, but the damage buff can stack.
Isaac deals 20 contact damage to enemies, twice per second. Does not prevent Isaac from taking contact damage.
If an enemy is at 40 HP or less, the contact damage is increased to 40 for that enemy.
Isaac's tears become red for the current room.
This item belongs to the Leviathan set. Collecting three items from this set will transform Isaac into Leviathan.
Notes
Isaac makes a demon sound when taking damage while this item is in use. This is quieter than Isaac's standard damage sound and is easy to miss.
Synergies
Book of Virtues: Spawns black wisps on the inner ring. Wisps shoot nails that deal double damage from standard wisps and have increased knockback, akin to 8 Inch Nails.
3DS The icon of The Nail as seen on the lower 3DS screen.
Trivia
The item's effect is a reference to the Nail of Vlad item in Castlevania II: Simon's Quest; equipping it would allow Simon to break certain obstacles such as rocks.
In the original The Binding of Isaac, The Nail was unlocked by beating Mom's Heart three times.
Gives one 
Soul Heart, +0.7 damage, -0.18 speed, and the ability to destroy most obstacles by walking into them. Cannot be stacked in one room.
Gives half a 
Black Heart, +2 damage, -0.18 speed and the ability to destroy obstacles for the current room.
This item belongs to the 
Leviathan set. Collecting three items from this set will transform Isaac into Leviathan.
Book of Virtues: Spawns black wisps on the inner ring. Wisps shoot nails that deal double damage from standard wisps and have increased knockback, akin to 
8 Inch Nails.
Sulfur.
Azazel Unlocks 
Boss Rush Unlocks 
The Binding of Isaac: Rebirth
