Ithani. Liminal Sky: Oberon Cycle, #3

Time is running out. After saving the world twice, Xander, Jameson and friends plunge headlong into a new crisis. The ithani?the aliens who broke the world?have reawakened from their hundred millennia-long slumber. When Xander and Jameson disappear in a flash, an already fractured world is thrown into chaos. The ithani plans, laid a hundred thousand years before, are finally coming to pass, and they threaten all life on Erro.
Venin and Alix go on a desperate search for their missing and find more than they bargained for. And Quince, Robin and Jessa discover a secret as old as the skythane themselves. Will alien technology, unexpected help from the distant past, destiny and some good old-fashioned firepower be enough to defeat an enemy with the ability to split a world? The final battle of the epic science fiction adventure that began in Skythane will decide the fate of lander and skythane alike. And in the north, the ithani rise..