Shadowbred. The Twilight War

A new trilogy starring Erevis Cale: On the edge of a war that will change the face of Faerûn, the world finds that not all shadows serve Shade Enclave In the wake of the battle, Erevis Cale and his companions-fellow Mask agent Drasek Riven and the half-human, half-demon Mags Kest-have settled into a more peaceful existence. But secretly, Cale is in turmoil. With his transformation into a shade nearly complete, he grasps at the last scraps of his physical humanity.
More than ever, he is like the master that he serves. But soon, fresh dangers are afoot. The goddess Shar has made the first move in her ploy to incite the Shadowstorm, a prophesied event that will reshape Faerûn according to her and the Shades' dark whims. As her agents sow the seeds of war throughout the realm, Erevis Cale and his companions-both old and new-must find a way to stop them in their tracks before the ancient Netheril empire can rise again.