It's hard to tell which came first, the fear of the number 13 or the unfortunate incidents surrounding it. It's entirely possible the number carries some ill fate with it, but it's also possible that the negative psychic association with it turned it into a self-fulfilling prophecy of sorts. It's this reason that the 13th floor of many apartment buildings and hotels are either relabeled or left empty. This superstitious trapping draws much attention from paranormal entities who use the fear associated with it to fuel their endeavors in these locations. The wall between the physical and ethereal planes in these places can be quite thin as a result.