Black Fireball

A beam of black light flashes from your pointing palm, then condenses to linger at a chosen point within range as a glowing bead the swirls with chaotic dark flames for the duration. Initially the flames occupy a sphere with a radius of 5 feet. At the end of each of your turns the flames expand by 10 feet (Max radius of 50 feet) and spread around corners. When a creature enters the area for the first time on a turn or starts its turn there, it must make a Dexterity saving throw. On a failed save, the creature takes 3d12 fire damage and 3d12 necrotic damage. On a successful save, the target only takes the fire damage.

At Higher Levels. When you cast this spell using a spell slot of 8th level or higher, the base damage increases by 1d12  fire damage for each slot level above 7th.