Crystal Shackles

Waves of crystal dust washes over a creature or object of your choice that you can see within range, forming sharp crystals around the floor that entwine the base of the target and pierce it. The target must make a constitution saving throw. The target takes 6d8 piercing damage on a failed save, or half as much damage on a successful one.

Additionaly it can't move without taking an additional 2d8 piercing damage, for the first time it tries to move again.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th. You can allocate the additional damage to either the initial damage or the damage done when moving through the crystals.