Daemonology: The Horus Heresy Series (Unabridged‪)‬

Chagrined by his defeat at the hands of Jaghatai Khan, Mortarion abandons the pursuit of the White Scars and instead leads the Death Guard in a spiteful, punitive rampage across the systems of the Prosperine empire.

World after world has fallen to this horrific onslaught, and yet the insular and secretive primarch seems preoccupied by some other unspoken goal. Finally, on Terathalion, the truth of Mortarion's sinister heritage will be exposed, and the future of the XIV Legion will be written....