Evard's Black Tentacles

Dark, writhing tentacles fill a 20-foot square on ground that you can see within range. For the duration, these tentacles turn the ground in the area into difficult terrain.

When a creature enters the affected area for the first time on a turn or starts its turn there, it must make a Dexterity saving throw. On a failed save, the creature takes 3d6 bludgeoning damage and is restrained by the tentacles until the spell ends. A creature that starts its turn in the area and is already restrained by the tentacles takes 3d6 bludgeoning damage.

A creature restrained by the tentacles can use its action to make a Strength or Dexterity check (the creature’s choice) against your spell save DC. On a success, it frees itself.