Legion

You call down a legion of shadowy soldiers in a 10-foot cube. Their features resemble a mockery of once-living creatures. Whenever a creature starts its turn inside the cube or within 5 feet of it, or enters the cube for the first time on its turn, the conjured shades make an attack using your melee spell attack modifier; on a hit, the target takes 3d8 necrotic damage. The space inside the cube is difficult terrain.