I wouldn't, because although I believe that there are multiverses, I don't believe that there is any way to go from any of them to any other. And if there were, witchcraft certainly wouldn't work, because that's a myth. However, if you really want to publish something like that, I'd recommend Amazon KDP. It's completely free, and I actually published a short story ("Well Met") based on the idea of traveling to alternative versions of our own universe, and received a number of reaquests to make that story the prologue to a novel based on the short story, and neither the short story or a novel based on it cost (or would cost) a penny. The only disadvantage is that if you want any copies to he read or sold, you need to do a lot of hard work to push it in the public's face.