Denno's Crystal Burst

You fire a splinter of crystalline magic at a creature you can see. Make a ranged spell attack against the target. On a hit, they take 8d8 piercing damage and are Restrained for the duration as sharp crystals grow around them. At the beginning of each of the creature's turns, they take 1d8 piercing damage from the crystals. The creature or one of their allies may make a Strength check against your spell save DC as an action, destroying the crystals and freeing the creature on a success.

When cast at higher levels, the initial damage increases by 1d8 for each level above 4th.