Stone Monsters (Only the Inevitable, #7)

Terrible monsters roam the city of Xanadu at night, and the populace lives in fear. The gateway only opens one direction. For the first time, David is alone, with no hope for help.

There is a prophecy involving Xanadu, but David knows nothing about it. All he knows is that the monsters here seem familiar. And that he's the only one who can stop them.