Viscous Vitriol

 A gob of viscous, caustic tar races towards a point you can see within range, detonating in a 20 foot radius sphere. Creatures in the area must make a Dexterity saving throw or be restrained as the slime coats them. Restrained creatures can use their action to remove the slime, freeing themselves; another creature can also use its action to remove the slime. Creatures that begin their turn coated in the slime take 4d4 acid damage.

The ground where the sphere detonated becomes difficult terrain. Creatures that end their turn in this area take 2d4 acid damage. After an hour, the slime dries and is no longer considered difficult terrain.

 At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d4 for each slot level above 3rd. This applies to both instances of damage.