Zombie Horde

You create a horde of nearly endless, but temporary, zombies. You destroy the target thrall, and the zombie horde appears in a 10-foot burst, which must include a square the destroyed thrall occupied. All squares on the ground in the zombie horde are difficult terrain. Whenever a creature begins its turn in the horde, it takes 3d4 bludgeoning damage with a basic Fortitude save.

Once per round on subsequent turns, you can Sustain the spell to move the horde up to 15 feet. At the start of each of your turns, all of your thralls in the horde are destroyed, and the area's burst increases by 5 feet for each thrall destroyed (to a maximum of a 30-foot burst). You can Dismiss this spell.