Corpse Explosion

You curse a corpse or willing undead within range, infusing it with a vile magic. It then bursts into a violent explosion  of writing black goo.  All creatures within 10ft of it must make a dexterity saving throw. A creature takes 3d6 necrotic damage on a failed save and half as much on success.

If your class gives access to Essence of Death: If there is a corpse within the area of the explosion or the explosion kills a creature, you can expend an Essence dice to continue the explosion with no extra action or spell slot cost, continuing the chain of explosions.