Thia's Arcane Breath

You drink from "Thia's Magic Mug" and imbue yourself with the power to spew magical energy from your mouth. Choose acid, cold, fire, lightning, or poison. Until the spell ends, you can use an action to exhale the chosen type of energy in a 20-foot cone. Each creature in that area must make a Dexterity saving throw, taking 6d6 +10 damage of the chosen type on a failed save, or half as much damage on a successful one.