Hammerfall - C. J. Cherryh

The Hugo Award–winning author and SFWA Grand Master delivers the first Gene Wars novel and "a brand-new universe with brand-new rules" (The San Diego Union Tribune).
In this brilliant novel—possibly Cherryh's masterwork—the fate of billions has come down to a confrontation between two profoundly alien cultures on a single desert planet.
Marak has suffered the madness his entire life. He is a prince and warrior, strong and shrewd and expert in the ways of the desert covering his planet. In the service of his father, he has dedicated his life to overthrowing the Ila, the mysterious eternal dictator of his world. For years he has successfully hidden the visions of a silver tower that plague him, but when his secret is discovered, Marak is betrayed by his own father and forced to march in an endless caravan with the rest of his world's madmen to the Ila's city of Oburan.
Instead of death, Marak finds in Oburan his destiny, and the promise of life—if he can survive an impossible mission given to him by the strange people in the towers.
According to these beings who look like him yet act differently than anyone he has ever known, Marak has a slim chance to save his world's people from the wrath of Ila's enemies. But to do so, he must convince them all—warring tribes, villagers, priests, young and old, as well as the Ila herself—to follow him on an epic trek across the burning desert before the hammer of the Ila's foes falls from the heavens above.
"C. J. Cherryh remains at the top of her game." —Tulsa World