Dark Fireball

This spell can be considered both a School of Necromancy Spell and a School of Evocation Spell

A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into an explosion of flame and necrotic energy. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 12d6 fire or necrotic (or a combination of the two) damage on a failed save, or half as much damage on a successful one. When you cast this spell that affects other Undead creatures that you can see, you can choose a number of them equal to 1 + this spell's level. The chosen creatures automatically succeed on their saving throws against the spell, and they take no damage if they would normally take half damage on a successful save. When you reduce a hostile creature to 0 hit points with this spell, you gain temporary hit points equal to twice your wizard.

The fire spreads around corners. It ignites flammable objects in the area that aren't being worn or carried.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d6 for each slot level above 5th.