Corpse Explosion

You can cause a violent explosion of essence inside a corpse. As an action you can explode a medium corpse. Every creature within 20 feet of the corpse must make a Dexterity saving throw. The creature takes 8d6 necrotic damage on a failed save, or half as much on a success. You can target an additional corpse within 20 feet of the first corpse as a chain of detonations 

At higher levels: For every level above 4th the spell can target one more corpse as long as it is within 20 feet of another detonated corpse.