Cruel Desperation

Target any living creature within 60 feet of you.
That creature has to make an Intelligence saving throw, taking 6d6 necrotic damage on a failed save or half as much on a successful one. If the targeted creature dies from this damage, the remnants of its life energy manifest in a dark burst, afflicting all living creatures in a 30 foot radius around the target with the spells initial effect again.

When you cast the spell at 6th level or higher, the necrotic damage increases by 1d6 per spell level above 5th.