Seeing a comrade in trouble, you interpose yourself to stop a painful blow.

Encounter   ✦     Martial
Immediate Interrupt      Melee 1

Trigger: An ally adjacent to you is hit by an attack.

Target: The triggering ally

Effect: The target gains a +2 power bonus to AC and Reflex against the triggering attack. If you are using a shield, the bonus increases to +4.

Published in Player's Handbook, page(s) 82, Class Compendium.