6th-Level Necromancy
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 8d6 necrotic damage on a failed save, or half as much damage on a successful one.
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.
Player's Handbook (2014), p. 221