PHB, page 250
Hellish Rebuke
1-level Evocation
Casting Time: 1 reaction, which you take in response to being damaged by a creature within 60 feet of you that you can see
Range/Area: 60 feet
Components: V, S
Duration: Instantaneous
Attack/Save: Dexterity Save
You point your finger, and the creature that damaged you is momentarily surrounded by hellish flames. The creature must make a Dexterity saving throw. It takes 2d10 fire damage on a failed save, or half as much damage on a successful one.
At higher levels: When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d10 for each slot level above 1st.
Available for: Warlock