A ghostly pale ray springs from your finger to an Undead or a creature with the Incorporeal Movement trait that you can see within range. The target must make a Constitution saving throw, taking 4d6 radiant damage on a failed save, or half as much damage on a successful one. If the target has the Incorporeal Movement trait and failed the saving throw, it is marked with magic that slowly unravels its spectral body for the duration.    At the start of each of its turns, the marked target must make a Constitution saving throw. On a failed save, it takes 2d6 radiant damage. On a successful save, the spell ends.