Armor of Agathys

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. 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 Material component is Cup of water