Jack of Harts

There are so many otherworlds in our religions.  There are so many other races.  Elves.  Dwarves.  Leprechauns.  Djinn.  Angels, Demons, and Gods.  Almost every religion in the history of our world preaches that there are other worlds and other races.  The questions I ask myself are whether these were just stories they made up, as many would have us believe, or did they actually, truly know something that we forgot?  And how do we find out?