Cask of Magdah (Ebonne)

You create a rattling Iron Maiden around one creature you can see within range. That creature must make a Strength saving throw. On a failed save, a creature takes 12d6 piercing damage and is restrained until the start of your next turn. On a successful save, the target takes half as much damage and isn't restrained. 

 At Higher Levels. When you cast this spell using a spell slot of 7th level or higher, the damage increases by 2d6 for each slot level above 6th.