I was doing some reading in the royal archives and I managed to put together some interesting information. (more after the jump)
There aren't any books that say it explicitly, but they all imply similar things. The people here didn't originally live on this planet. They on what I believe to be Earth. Thousands of years ago, facing massive persecution, four great mages combined their power to open the pathway to a new world. They brought many other mages with them. The new world, however, didn't allow them to use magic. So, they somehow managed to bring whatever it was that gave them magic in the old world over to the new one. They vowed never to return, but they could never figure out how to close the Passage, as they call it.