Burning Ash
The coven sprays black ash across a 40-foot radius. Each creature in the area makes a Constitution saving throw against your spell save DC. On a failure it takes (H + half your level)d10 fire damage and is Blinded. On a success it takes half damage and is not Blinded. A creature Blinded this way repeats the saving throw at the end of each of its turns, ending the condition on a success.
Blinded: the creature cannot see and automatically fails any check that requires sight. Attacks against it have advantage, and its own attacks have disadvantage.
The spell leaves a lingering ash cloud for 10 minutes. A creature that enters the cloud or starts its turn there makes the same Constitution saving throw, taking 1d6 fire damage and becoming Blinded on a failure, or half damage and no blindness on a success. The blindness ends at the end of a turn on which it succeeds, or when it leaves the cloud.
Any fire damage striking the cloud detonates it. Each creature inside makes a Dexterity saving throw against your spell save DC, taking 5d8 fire damage on a failure and half as much on a success. The lingering cloud then ends and every Blinded creature recovers.

