The blow seems to rend your body completely, and the remnants burn with blue flame. Then you strike your enemy from behind.

Daily   ✦     Arcane, Teleportation
Immediate Reaction      Personal

Trigger: You take damage from an attack

Effect: You disappear. At the start of your next turn, you reappear in any unoccupied space within 5 squares of the creature that attacked you, and the creature that attacked you grants combat advantage to you until the end of your next turn.

Published in Forgotten Realms Player's Guide, page(s) 43.