I’ve been on an acid kick lately. How about a new version of fireball mixed with acid arrow?
Casting Time: 1 action
Range: 150 feet
Components: V, S, M (a ball of slug slime)
With a flick of the wrist you throw a blob of acid toward a target within range. Make a ranged spell attack against the target. On a hit, the target takes 4d6 acid damage, and all each creature in a 20-foot-radius sphere centered on the first target must make a Dexterity saving throw. A target takes 4d6 acid damage on a failed save. All targets damaged by this spell are covered in acid and must make a Dexterity saving throw at the start of their turns or take 4d6 acid damage each round until they succeed on a saving throw at the start of their turns to removed the acid and end the effect or remove the acid as an action. If the initial ranged spell attack misses, there are no additional effects.
At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.