Your attack addles your foe, causing it to focus on you instead of on your friend. With a little more effort, you can force your enemy to focus solely on you.

At-Will   ✦     Augmentable, Psionic, Weapon
Standard Action      Melee weapon

Target: One creature

Attack: Constitution vs. AC

Hit: 1[W] + Constitution modifier damage, and one ally within 5 squares of you becomes invisible to the target until the target is adjacent to him or her or until the end of your next turn.

Augment 1

Hit: As above, but the invisibility isn't ended by the target being adjacent to the ally.

Augment 2

Hit: 2[W] + Constitution modifier damage. Until the end of your next turn, your allies are invisible to the target while they aren't adjacent to it.

Published in Player's Handbook 3, page(s) 46.