The City by Stella Gemmell

In her debut solo novel, Stella Gemmell, coauthor of the conclusion to David Gemmell’s Troy series, creates a dark epic fantasy set in a war-torn civilization ruled by an immortal emperor. 
The City, once a vibrant metropolis, has become a barren wasteland due to endless wars. Few have seen the emperor, who appears ageless and is rumored to be something other than human. The desperate believe that ending his long life is the key to stopping the conflict.
From the sewers where the poor endure darkness to the blood-soaked battlefields, rebels place their hopes on Shuskara, the emperor’s former general, thought to be dead but now in hiding. He must engage in one final battle to liberate the City from the creature at its heart, responsible for the ongoing bloodshed.