Artificer Utility 2Bolster Armor

You touch some armor, causing it to glow as you enhance its defenses.

Daily        Arcane
Minor Action      Melee touch

Target: You or one ally

Effect: The target gains a +1 power bonus to AC until the end of the encounter. When hit by an attack, the target can end this bonus as a free action to gain a +4 bonus to AC against that attack.

Update (11/23/2009)
Add “until the end of the encounter” to the end of the first sentence.

Published in Eberron Player's Guide, page(s) 48.