Charnel Fire

With sinister flame and brimstone, the caster completely consumes one dead body so that absolutely nothing remains. A creature whose body is destroyed by a this spell can only be brought back to life through a true resurrection spell. This spell can also be cast on corporeal undead with a CR of 1 or lower, who must succeed on an Intelligence saving throw to avoid being destroyed.

At higher levels. When cast with a 6th level spell slot, this spell can be cast on corporeal undead with a CR of 2 or lower. With an 8th level spell slot, this spell can be cast on corporeal undead with a CR of 3 or lower. Finally, with a 9th level spell slot, this spell can be cast on corporeal undead with a CR of 4 or lower.