"I don't get it," Jake said. "How come the fortress and the portal don't change but everything else does?" he asked as they found themselves walking across a snowy tundra suddenly.<br/><br/>"Because they are the only physical things here other than us," Merlin replied. "The infinite realm is like a giant flux, if you stayed here long enough you'd probably find yourself walking on thin air, or what looked like thin air anyway."