The Clavis (The Emperor's Library: Book Four) - The Emperor's Library, #4

After the events of The Game, Jon and Sem traveled to Drom and brought back inventions that made Tarnak a wealthy city. Sem is dead, but, thanks to the tritargons, both Jon and Klei remain alive, although very old. Jon has become a recluse, refusing to see even his own servants, while Klei now lives with the descendants of the Rand at the Forest House. The Clavis is the story of Rel, a handsome, unrelentingly polite young man from a small town east of Tarnak.
It begins with his arrival to work for his uncle in the city, where Billy, a gay co-worker, shows him the town and takes him to a remarkable restaurant. Sent on a sales journey to the Southlands, Rel encounters Klei, who gives him a letter to deliver to Jon, and this letter transforms his life. Jon insists upon seeing the messenger and, after a long conversation in which he explains the history of life on the planet, impulsively gives him a mysterious object (the clavis) to hide in his family's orchard.
Thus commences a chain of events that bring a violent end to most of Rel's family and lead Rel himself into slavery. Eventually, Rel, Billy and Rel's sister Kara, along with his brother Max, the Empress Ktoressa, and an assortment of other characters, find themselves at the ruined city of Kar. Here, where the fate of humanity hangs in the balance, the final, breathtaking, events of the novel unfold.