Corrosive sphere

You hurl a sphere of corrosive liquid to a target in range. On a hit, the target takes 1d6 acid damage. The liquid then covers a 15ft x 15ft area with bubbling acid, centred on the target. Any creature that starts its turn, or moves into the area takes 1d4 acid damage. The area is covered for as many rounds as the casters proficiency bonus.

This spell's damage increases by 1d6 and 1d4 when you reach 5th level (2d6 and 2d4), 11th level (3d6 and 3d4), and 17th level (4d6 and 4d4).