Coil of Hadar

You cause dark, inky tendrils to reach up from the ground and envelop a creature you can see within range. The creature must make a Strength saving throw. On a failed save, it takes 4d8 necrotic damage and is restrained until the spell ends. On a success, it takes half as much damage and is not restrained.

A creature restrained by this spell repeats the saving throw at the end of each of its turns. The same damage detailed above applies for failed and successful saves.

As an action on your turn, if the summoned tendrils are not restraining a creature, you can choose a creature you can see within range and target that creature.

Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 4.