Your shot hinders an enemy and gives its would-be target the perfect opportunity.

Daily   ✦     Arcane, Weapon
Immediate Interrupt      Ranged weapon

Trigger: An enemy within range makes an attack roll against an ally

Target: The triggering enemy

Attack: Charisma vs. Reflex

Hit: 3[W] + Charisma modifier damage. The ally who was attacked by the triggering enemy can make an at-will attack against that enemy as a free action. The ally gains a bonus to this attack roll equal to your Wisdom modifier (minimum 1).

Miss: Half damage.

Published in Arcane Power, page(s) 7.