Death’s Dark fertility

When you cast this spell you create either your choice of a  160’ x 160’ cube or 80’ x 360’ rectangle which is briefly filled with a black wind. Each creature in the affected area must make a constitution saving throw or take 20d8 necrotic damage on a failed save or half as much on a success. 

Any creature of size large or small that is killed by this spell raises as a zombie permanently under your control at the start of its next turn. No more then 500 total hit points worth of zombies can be created by a single casting of this spell.