Kartan's Void RingLevel 26 Uncommon

The shifting form of this black ring allows you to draw off your enemies' vigor when one of their nearby allies drops.

Ring Slot        1,125,000 gp

Power (Healing, Necrotic) At-Will (Free Action)

Trigger: You reduce an enemy within 20 squares of you to 0 hit points.

Effect: Make an attack: Area burst 2 centered on that enemy; targets enemies; +29 vs. Fortitude; on a hit, the attack deals 1d10 necrotic damage, and you regain 2 hit points. This attack doesn't provoke opportunity attacks.
    If you've reached at least one milestone today, the attack deals 2d8 necrotic damage, and you regain 4 hit points.

Published in Adventurer's Vault 2, page(s) 137.