The light dims in a location you specify within range, shadows consuming the light. Until the spell ends, a 30-foot-radius, 40-foot-high cylinder dulls the light within it. Within the cylinder, areas of normally bright light become dim light, areas of normally dim light become darkness, and areas of normal darkness become magical darkness.   When the cylinder appears, each undead creature within the cylinder gains 1d12 temporary hit points and each non-undead creature within the cylinder takes 1d12 necrotic damage. While a non-undead creature is in the cylinder, it takes an additional 1d12 necrotic damage the first time it takes damage each turn. Undead creatures who end their turn in the cylinder gain 1d12 temporary hit points.   If you’re within 60 feet of the cylinder, you can move it up to 60 feet as a bonus action on your turn. If the spell’s area ever overlaps with the area of a dawn spell, both spells immediately end.