You keep your distance from an approaching adversary, backpedaling easily away from him.

Daily   ✦     Martial
Immediate Interrupt      Personal

Trigger: An enemy moves adjacent to you

Effect: You can shift 1 square and then move a number of squares equal to 1 + your Wisdom modifier. You can't end your move adjacent to the triggering enemy.

Published in Player's Handbook, page(s) 109.