Black smog

You create a 20-foot-radius sphere of purple, reeking smog centered on a point within range. Each creature within the sphere must succeed on a Constitution saving throw or take 3d8 poison damage and become poisoned until the spell ends. While poisoned in this way, the target is also blinded. A creature may re-attempt this save at the end of their turn, ending the effect on a success.

On a successful save, the target takes half the damage and is not poisoned.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, increase the poison damage by 1d8 for each slot level above 4th.