Circle of Plague

A sphere of swampy air 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 3d6 necrotic damage on a failed save as well as being poisoned , or half as much damage on a successful one. 

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 2d6 for each slot level above 3th.