You respond to an enemy's attack with a riposte, and you call for an ally to join you against the offender.

Encounter   ✦     Martial
Immediate Reaction      Personal

Trigger: An enemy hits you

Effect: You make a basic attack against the triggering enemy, and one ally within 5 squares of you can move his or her speed and make a melee basic attack against the triggering enemy as a free action.

Published in Martial Power 2, page(s) 85.