Aquar's Abyssal Grasp

Spectral tentacles burst from the ground and latch on to a creature of your choice that you can see within range. The target must succeed on a Strength saving throw or be restrained for the duration. At the end of each of its turns, the target can make another Strength saving throw. On a success, the spell ends on the target.

For the spells duration you can use your bonus action to inflict 2d8 Cold or Lightning  damage (Your choice when dealing the damage) to the restrained creature.

If a creature is killed by  this spell you can use your reaction to immediately target another creature within range

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the spell deals one extra d8 for each slot level above 2nd.