A swarm of flying, bat-like shapes swirl into existence in a 20-foot-radius cloud around the point you target your spell. Each round a creature begins its turn in the swarm, it takes 4d8 necrotic damage and must succeed on a Wisdom saving throw or become frightened for 1d4 rounds. Creatures that are immune to necrotic damage are not susceptible to the frightened effect. You can use an action on your turn to move the swarm up to 40 feet in any direction.