There is an infinite number of different worlds, all filled with magic; you become able to travel between them at will, become the most gifted magician in any of them, you do not age unless you wish so, dying will revive you at different world unless you wish to die completely.

You can only travel between worlds alone, you can't stay in any world for more than one month, you can't control your destination(it's chosen at random) and you can't return back to any world you've already been in. These rules can't be bypassed in any way.