The Infernal City — Greg Keyes

Four decades after the Oblivion Crisis, Tamriel is threatened anew by an ancient and all-consuming evil. It is Umbriel, a floating city that casts a terrifying shadow-for wherever it falls, people die and rise again.

And it is in Umbriel's shadow that a great adventure begins, and a group of unlikely heroes meet. A legendary prince with a secret. A spy on the trail of a vast conspiracy. A mage obsessed with his desire for revenge. And Annaig, a young girl in whose hands the fate of Tamriel may rest . . . .