Boneshaker

You violently take control of a living creature’s skeleton, rattling it within its flesh. The target must make a Constitution saving throw, taking 3d6 bludgeoning damage on a failure, or half as much damage on a success. Because damage from this spell is caused internally, it cannot be reduced by any means.

At Higher Levels. When you cast this spell using a spell slot of 3rd-level or higher, the damage increases by 1d6 for each slot level above 2nd.