Dragon's Breath

You touch one willing creature, and choose Acid, Cold, Fire, Lightning, or Poison. Until the spell ends, the target can take a Magic action to exhale a 15-foot Cone. Each creature in that area makes a Dexterity saving throw, taking 3d6 damage of the chosen type on a failed save or half as much damage on a successful one.

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 2.