A thin sheet of flames shoots forth from you. Each creature in a 15-foot Cone makes a Dexterity saving throw, taking 3d6 Fire damage on a failed save or half as much damage on a successful one.
Flammable objects in the Cone that aren't being worn or carried start burning.
Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 1.