Encroaching Shadows

You cause menacing shadows to invade an area 200 feet on a side and 50 feet high, centered on a point within range. Illumination in the area drops one step (from bright light to dim, or from dim light to darkness). Any spell that creates light in the area that is cast using a lower-level spell slot than was used to cast encroaching shadows is dispelled, and a spell that creates light doesn’t function in the area if that spell is cast using a spell slot of 5th level or lower. Nonmagical effects can’t increase the level of illumination in the affected area. A spell that creates darkness or shadow takes effect in the area as if the spell slot expended was one level higher than the spell slot actually used.