Can monsters use the Secret Stairs, Secret Passage, Revolving Wall, and Mystic Slide to move around?
Yes. It’s their house, after all. (Besides, it’s possible for these to create areas of the house that can’t be reached any other way, and some scenarios won’t work if monsters can’t reach all rooms.) Ignore the section of the rules that states, “unless those cards state that only explorers can use them.” Also, a monster wouldn’t need to roll to use the revolving wall.