Bog Breath

Your breath becomes caustic, choose Acid or Poison. Until the spell ends, you can take a Magic action to exhale a 15-foot Cone. Each creature in that area makes a Dexterity saving throw, and on a failed save a creature takes 3d6 damage of the chosen type, and becomes coated. A creature is not coated and takes half as much damage on a successful save. Coated creatures take an additional 1d6 damage of the chosen type at the start of each of its turns unless it spends an action removing the coating or is submerged in water or similar liquid.

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