Acid Pike

You brandish the weapon used in the spell’s casting and make a melee attack with it. On a hit, the target suffers the weapon attack’s normal effects and acid splashes from your weapon and creates a pool 5 feet in diameter on the ground beneath the creature's feet. The pool of acid lasts for the spell's duration, and any creature that ends its turn in that pool takes 1d8 acid damage.

At Higher Levels. At 5th level, the melee attack deals an extra 1d8 acid damage to the target on a hit, and the damage the target takes from ending its turn in the acid pool increases to 2d8. Both damage rolls increase by 1d8 at 11th level (2d8 and 3d8) and again at 17th level (3d8 and 4d8).