Aside from the obvious (scary and evil), I think it would make sense for each realm to have some other "feeling" associated with it depending on the theme. Since The Ivory Labyrinth makes it harder to navigate or tell directions, I would say something like "As you enter the Ivory Labyrinth you are overcome with the greatest feeling of being lost you've ever known." I'm not sure for the Midnight Isles or Rasping Rifts, though.