Bone armor

A sphere of negative energy ripples out in a 60-foot-radius sphere from a point within range. Each creature in that area must make a Constitution saving throw. A target takes 6d6 necrotic damage on a failed save, or half as much damage on a successful one. 

In addition, the caster may add half the damage rolled in temporary hit points and gain +2 AC for 1 minute.

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.