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.

Notes

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. This is not generally recommended, as it will make it difficult to gain damage off of targets.
- Dark Arts still works on reflected bullets, which may be beneficial.
- Explosive projectiles will explode when destroyed by Dark Arts, unlike those destroyed by Lost Contact.
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 will trigger certain tear effects on enemies it damages, such as burning from Fire Mind.
Dark Arts is extremely effective against enemies with multiple segments such as Larry Jr. because it can affect each segment individually, greatly increasing damage.
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 still deal damage, making the fight significantly easier.
Dark Arts can be a useful tool for Tainted Jacob to avoid colliding with Dark Esau, as the invincibility and stunning effects of the item fully work against him even if Esau charges at the player.
Dark Arts is fantastic in Greed mode. It can be used to press the button without taking any damage, kill many enemies with each activation, and have the item be constantly recharged with each wave.
- While playing as Tainted Judas, each enemy or projectile ran into will grant a damage buff. With the sheer amount of enemies appearing, especially in Greedier, Tainted Judas will gain an immense damage buff and can kill huge swaths of enemies with ease. Additionally, this is even more potent against Ultra Greed, as you can run through the many Greed Gapers summoned to gain even greater damage buff, as the Gapers will be clustered very closely together.

Synergies

Items that trigger on kill like Athame, Vasculitis, Bone Spurs, etc. will make Dark Arts deal more damage.
9 Volt: Halves the time required to charge Dark Arts, making it usable every 3 seconds.
120 Volt/Jupiter/Monstrance/Salvation/knife given by the Yes Mother? transformation: These items stay in effect even while using Dark Arts, allowing Isaac to deal more damage to nearby enemies while invulnerable.
Backstabber: Tagging an enemy from behind will apply Backstabber's effect.
The Battery: Second charge can be used while Dark Arts is active, essentially making it last longer.
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.
Car Battery: Dark Arts will last twice as long, totaling at 2 seconds per use.
Euthanasia: When Dark Arts ends, each enemy tagged may instantly die and release a burst of black tears as if hit by a Euthanasia tear.
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: Jumping over an enemy or projectile while Dark Arts is active will tag it.
Ipecac: Because Dark Arts' damage is scaled off of tear damage, Ipecac gives an extremely high damage boost to each Dark Arts hit.
Kamikaze!: Kamikaze! can be activated without harm while using Dark Arts.
Maw Of The Void/Montezuma's Revenge/Revelation: Can be charged and released during Dark Arts.
Mom's Knife/ Yes Mother?: The knife will still deal damage even while in Dark Arts.
Pause: Activating Dark Arts will not cancel the effect.
- Pause + 9 Volt: Pause can be used every room, making most of them very easy to clear.
Saturnus: Orbiting tears are able to damage enemies during Dark Arts.
Taurus: Dark Arts' speed increase will contribute towards Taurus' activation, allowing Isaac to become invulnerable much earlier.
Wisps: Wisps cannot be destroyed while Dark Arts is in effect and still deal contact damage.

Interactions

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.
Libra: Not recommended. The speed boost during the invincibility phase is transferred into other stat bonuses, which are useless as tears cannot be used. If used with Tainted Judas or Dark Judas, the temporary damage boost is divided across all of his stats, resulting in negligible stat boosts.
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. They're likely to hit any enemies or projectiles Isaac runs through without using the drop button to make them stay still.
Mars: Isaac is able to dash while using Dark Arts.

In-game footage

Trivia

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.

Bugs

Bug!	Sometimes, if the player touches an enemy, Dark Arts can last shorter and end prematurely.^{[Check ingame]}

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.