With a calculated strike, you leave your foe vulnerable to an adroit riposte if it dares to attack you.

At-Will   ✦     Martial, Weapon
Standard Action      Melee weapon

Requirement: You must be wielding a light blade.

Target: One creature

Attack: Dexterity vs. AC

Hit: 1[W] + Dexterity modifier damage. If the target attacks you before the start of your next turn and it is within reach, you can make a Strength vs. AC attack against it as an immediate interrupt. On a hit, the target takes 1[W] + Strength modifier damage.
    Level 21: 2[W] + Dexterity modifier damage and 2[W] + Strength modifier damage.

Update (9/30/2011)
Updated in Class Compendium.

Published in Player's Handbook, page(s) 118, Class Compendium.