Coil of Hadar

You cause dark, spectral tentacles 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 failure it takes 4d8 necrotic damage and is restrained until the spell ends. On a success, it take half as much damage and isn't restrained.

A creature restrained by this spell repeats the saving throw at the end of each of its turns, it takes 4d8 necrotic damage and is still restrained on a failure, or half as much and is no longer restrained on a success.

As an action on your turn, if the summoned tentacles aren't restraining a creature, you can choose a creature you can see within range, and force that creature to make a Strength saving throw, on a failure it is restrained by the tentacles as they spring up around it until the spell ends.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the spell's damage increases by 1d8 for each slot level above 4th.