Armor of Agathys

D&D 2014 spell: Armor of Agathys. Source: Player's Handbook (2014). level 1, school Abjuration, casting time 1 action, range Self (point), 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

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 level above 1st.

Source: Player's Handbook (2014), p. 215 - Licenses and attribution