The Last Portal. Black Iron Prophecies, #3

Portals are opening randomly across the realms; disaster looms. The network linking the worlds of humans and elves is collapsing. Portals are opening at random, threatening to tear reality apart and bring catastrophe to people on both sides of the Gap. The fear of impending doom drives the Queen to send her Mage Lord across the Gap to fix the problem. But things are never as easy as they seem. To fix the network, Rye, Pete and Yllmae must find a legendary book, unearth the long-lost master portal stones, and cast the right spell before the system experiences a devastating collapse.
And not everyone wants to see the network restored. A band of fanatics led by a wayward preacher want to close the portals permanently, and they're ahead of our heroes at every step. Can Rye and Yllmae find the master portal and prevent a disaster of global proportions?