Black Fireball

A maelstorm of swirling black fire appears near your hands. On your next turn, you can choose a spot within range as an action, provided this spell hasn't ended. The maelstrom disappears from your hands and reappears centered on that point, grown exponentially. Each creature in a 30-foot-radius sphere centered on the point must make a Dexterity saving throw. A target takes 6d6 fire damage and 6d6 necrotic damage on a failed throw and takes half as much damage on a success. The maelstrom spreads around corners. It ignites flammable objects in the area that aren't being worn or carried, and it withers nonmagical, normal plants.