You envelop your enemy in an inky cloak of shadow that writhes and coils around him, twisting her attacks against you.

Daily   ✦     Arcane
Standard Action      Ranged 5

Target: One creature

Effect: You place your Warlock's Curse upon the target. In addition, it must reroll any successful attack it makes while affected by your curse and take the new result.

Published in Player's Handbook, page(s) 140, Class Compendium.