Umbral Storm

You create a channel to a region of the Plane of Shadow that is inimical to life and order. A storm of dark, raging entropy fills a 20-foot-radius sphere centered on a point you can see within range. Any creature that starts its turn in the storm or enters it for the first time on its turn takes 6d8 necrotic damage and gains one level of exhaustion; a successful Constitution saving throw halves the damage and prevents the exhaustion.

You can use a bonus action on your turn to move the area of the storm 30 feet in any direction.