Unholy Balestorm

Summoning the unholy forces of the Abyss, a mass of swirling black flames flash into existence
A storm made up of sheets of roaring black flame and screaming souls appears in a location you choose within range. The area of the storm consists of up to ten 10-foot cubes, which you can arrange as you wish. Each cube must have at least one face adjacent to the face of another cube. Each creature in the area must make a Dexterity saving throw. It takes 7d10 Necrotic damage on a failed save, or half as much damage on a successful one.

The necrotic fire damages objects in the area, blights the land it touches.. all plant life withers and dies within 10 feet of the storm.