Warlock Attack 1Armor of Agathys
You surround yourself in a sheath of black ice from a dark and doleful realm. It protects you from attack and radiates fierce cold.
Daily Arcane, Cold
Standard Action Personal
Effect: You gain temporary hit points equal to 10 + your Intelligence modifier. Until the end of the encounter, an enemy that starts its turn adjacent to you takes 1d6 + Constitution modifier cold damage.
Published in Player's Handbook, page(s) 132, Class Compendium.