Corpsefire

You snap your fingers and cause a number of small or medium corpses to erupt with flame and be burnt to ash. You can target a number of corpses equal to your spellcasting modifier. All creatures within 10ft of the corpse must make a Dexterity saving throw. On a failed save, they take 3d8 fire damage, on a successful save they take half as much damage.

If you target an undead creature, they must make a Constitution saving throw, taking twice as much damage on a failed save, and the normal amount on a successful one. If it is taken to 0 hit points this way it is immediately reduced into ash.

At Higher Levels: When you cast this spell using a  4th level spell slot or higher, you may increase the damage dice by 1d8 or number of targets by 2 for each spell level above 3rd.