Alutar: the Great Demon — Richard S. Tuttle

Using the enemy's own portals, King Arik sends the elite forces of Alcea to Zara to crush the Federation. Woefully outnumbered, the Alceans join forces with the indigenous rebels to battle the massive armies of Emperor Jaar while the Knights of Alcea scheme from within the enemy's leadership to foil the Federation's ability to respond. While the world focuses on the battle between King Arik and the Federation, Fakir Aziz gathers the most powerful mages in Zara to carry his own battle directly to Alutar, the Great Demon. Should the Mage fail, all is lost. Alutar: the Great Demon is the seventh and final volume of the Demonstone Chronicles.