Mortarion

Mortarion, also known as the “Pale King,” the “Death Lord” or the “Prince of Decay” after he turned to Chaos, was one of the original twenty Imperial primarchs created by the Emperor of Mankind. He was given command of the Death Guard Space Marine Legion on the arrival of the Emperor to his homeworld of Barbarus, but he turned to the service of Chaos during the Horus Heresy. At present, Mortarion is the greatest Daemon Prince of Nurgle and the Daemon Primarch of the Death Guard Chaos Space Marines. He recently returned to Imperial space for the first time in ten thousand standard years when he led the forces of the Plague God in the invasion of the Realm of Ultramar during the Plague Wars.