Dark Arts

Dark Arts is an unlockable activated item added in The Binding of Isaac: Repentance. Tainted Judas starts with this item in his consumable slot.

Effects

When used, Isaac gains +1.0 speed and can walk through enemies/bullets for 1 second or until he shoots. If Isaac walks through an enemy or bullet during this time, it freezes until the effect ends, then takes damage equal to 2× Isaac's damage plus a flat 3.5. If there are multiple enemies/projectiles caught in the attack, each consecutive attack deals an additional flat 3.5 damage. At the end of the effect, an area of effect blast is created, dealing more damage the more enemies or bullets were pierced during the effect.
- The damage of the blast at the end of Dark Arts is equal to the sum of all damage dealt while dashing between enemies.
  - Bullets walked through will still count for the final blast damage calculation, even though they can't be damaged.
When used as Dark Judas or Tainted Judas, for every enemy/bullet he walks through, he will gain a temporary +1 damage bonus, which wears off at a rate of -0.25 damage every half second.

The invincibility can be canceled early by firing tears (and hence receive the damage bonus early with Tainted Judas or Dark Judas).
If an enemy/bullet Isaac walks through dies or otherwise disappears before Dark Arts deactivates, they will not grant a damage bonus.
Orbitals that deal contact damage such as Forever alone will still deal damage and potentially kill an enemy, while those that block shots like Pretty Flies will still block and destroy projectiles.
- Dark Arts still works on reflected bullets.
- Explosive projectiles will explode when destroyed by Dark Arts.
Isaac cannot pick up items or donate to Blood Donation Machines or Devil Beggars while Dark Arts is activated, but he can pass through Curse Room doors or over spikes.
Dark Arts cannot open Spiked Chests or Mimic Chests while active, but standing on the chests when the effect ends will safely open them.
Isaac can still press Pressure Plates while Dark Arts is activated.
- Dark Arts can be used to press the button in Greed Mode without taking any damage.
Dark Arts will trigger certain tear effects on enemies it damages, such as burning from Fire Mind.
Invincible enemies such as Stonies and Stone Grimaces can still be affected and used to increase the damage.
- Hosts can be damaged and killed even while they are lowered and invincible.
- Similarly, using Dark Arts on Scolex's invulnerable segments will deal damage.

9 Volt: Halves the time required to charge Dark Arts.
Backstabber: Tagging an enemy from behind will apply bleeding.
The Battery: Second charge can be used while Dark Arts is active.
The Book of Belial + Birthright as Judas / Dark Judas: Grants temporary damage ups for every enemy/projectile hit by Dark Arts, similarly to Tainted Judas. This stacks with Dark Judas' inherent version of this, doubling the amount of damage gained.
Book of Virtues: Spawns black wisps on the middle ring whenever an enemy is killed with Dark Arts. The wisps do not persist between rooms.
Camo Undies: The stealth mode given by Camo Undies won't be removed by activating Dark Arts. However, Dark Arts only gives +0.5 speed while Camo Undies is active.
Car Battery: Dark Arts will last twice as long, totalling at 2 seconds per use.
Euthanasia: Dark Arts can apply the Euthanasia effect.
Pause: Activating Dark Arts will not cancel the effect.
Taurus: Dark Arts' speed increase will contribute towards Taurus' activation.
Wisps: Wisps cannot be destroyed while Dark Arts is in effect.

Aries / E. Coli / Midas' Touch / Mom's Heels / Serpent's Kiss / The Virus: On-touch effects won't activate while Dark Arts is active.
Blood Oath: Using Dark Arts will block the damage, preventing Blood Oath from activating.
Gnawed Leaf: If Isaac is stationary when Dark Arts ends, he will gain invulnerability without any downtime. Dark Arts can also be used from invulnerability without taking damage.
How to Jump: Can be used while Dark Arts is active.
Kamikaze!: Can be activated without harm while using Dark Arts.
Lil Clot / Sumptorium: Clots gain increased speed and are no longer be able to fire, but are still vulnerable to damage while Isaac is using Dark Arts.
Mars: Isaac is able to dash while using Dark Arts.

The item is a reference to a flash game Edmund McMillen created in 2005 called Grey-Matter. In this game, enemies would be killed in a fashion identical to Dark Arts.
Before being added in game, Dark Arts was the starting item for Dark Judas in The Binding of Isaac: Four Souls, a card game created by Edmund McMillen.

Bug!	Using Dark Arts after using Doctor's Remote before the missile hits the ground will trap Isaac in the animation of holding the remote over his head until leaving the room or getting hit, preventing you from firing tears.

Bug!	If tagged during a dash attack, certain enemies and bosses will "dash" without actually moving after Dark Arts end. This is most notable for The Cage - the boss will roll in place for a couple of seconds. If such an enemy gains momentum in any way (e. g. via collision with other enemies, explosions, or knockback from Isaac's tears), it will resume the dash.