Spell Level: 1
Spell School: Evocation
Casting Time: 1 Reaction (which you take in response to taking damage from a creature that you can see within 60 feet of yourself)
Components: V, S
Range: 60 ft.
Area: None
Duration: Instantaneous
Conditions/Effects: Damage (Fire)
Saving Throw: Dexterity
Ritual: No
Scaling: Spell Slot Level
Classes: Warlock
Link: Link to source
The creature that damaged you is momentarily surrounded by green flames. It makes a Dexterity saving throw, taking 2d10 Fire damage on a failed save or half as much damage on a successful one.
Using a Higher-Level Spell Slot. The damage increases by 1d10 for each spell slot level above 1.