Player's Handbook
Armor of Agaythys
1-level Abjuration
Casting Time: 1 action
Range/Area: self
Components: V,S,M
Materials: a cup of water
Duration: 1 hour
A protective magical force surrounds you, manifesting as a spectral frost that covers you and your gear. You gain 5 temporary hit points for the duration. If a creature hits you with a melee attack while you have these hit points, the creature takes 5 cold damage.
At higher levels: When you cast this spell using a spell slot of 2nd level or higher, both the temporary hit points and the cold damage increase by 5 for each slot.
Available for: Wizards, Warlocks