Swift Riposte

Momentum power
At-Will (once per round)

You can't gain momentum from hitting with swift riposte.

Interrupt action; you must spend your momentum
An enemy targets you with a melee attack.

You can make a basic attack against your attacker. If your natural attack roll equals or beats your attacker's roll, resolve your basic attack against that enemy first. If your attack roll is lower, your attack has no effect, regardless of whether it hits or misses.

Champion Feat: 

If your swift riposte attack is a critical hit, the enemy's attack misses.

Epic Feat: 

You gain a +2 attack bonus with swift riposte attacks.