Armor of Agathys

1st-level 6. 🔧Mechanics/🪄 Magic/Schools Of Magic/Abjuration

Casting Time: 1 Bonus Action
Range: Self
Components: V, S, M (a cup of water or a shard of blue glass)
Duration: 1 Hour
Spell Lists: 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 each spell slot level above 1.

Source: PHB'24, page 243