Armor of Agathys

Player's Handbook (2024) p. 243

Level
1
School
Abjuration
Casting Time
Bonus Action
Range
Self
Components
V, S, M (a shard of blue glass)
Duration
1 hour
Classes
Warlock, Blood Hunter (Alt. LaserLlama) (Order of Witch Knights), Paladin (Conquest), Mark of Warding (Legacy)

Description

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.