Mike Lee
The Rise of Nagash

Nagash, priest king of Khemri, embarks upon a quest for immortality that will spark a war, destroy an empire and unleash a plague of undeath that will blight the world forever.
omnibus

It contains:
Nagash the Unbroken
Nagash the Sorcerer
Nagash Immortal

Also in:
Nagash: the Ebook Bundle
Legends of the World That Was