Armor of Agathys

Level & School
1st-level abjuration
Casting Time
Bonus action
Range
Self
Components
V, S, M (a shard of blue glass)
Duration
1 hour
Classes
Warlock

Protective magical frost surrounds you. You gain 5 Temporary Hit Points. If a creature hits you with a melee attack roll before the spell ends, the creature takes 5 Cold damage. The spell ends early if you have no Temporary Hit Points.

Using a Higher-Level Spell Slot. The Temporary Hit Points and the Cold damage both increase by 5 for cach spell slot level above 1.

Level & School
1st-level abjuration
Casting Time
Action
Range
Self
Components
V, S, M (a cup of water)
Duration
1 hour
Classes
Warlock

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.

Using a Higher-Level Spell Slot. 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.

Armor of Agathys 5.5e 2024 vs. 5e 2014 edition differences

The 2024 version adds that the spell ends early if you have no Temporary Hit Points, and clarifies that the Cold damage occurs if a creature hits you with a melee attack roll before the spell ends. Both versions increase damage and temporary hit points by 5 per spell slot above 1st level.