Codex: Chaos (1996), p12-13 — Death Guard

The Death Guard Legion was one of the original twenty Space Marine Legions founded by the Emperor. During the Horus Heresy the Legion joined the rebel Warmaster Horus and took part in many battles against the Emperor's forces. When Horus led his attack on the Emperor, the rebel Death Guard Legion was marooned in the warp while attempting the long journey to Earth. Days passed while the fleet's Navigators searched for a warp-tide that would bring them bak to the material universe. Meanwhile a mysterious contagion began to spread from ship to ship. The stinking pestilence bloated the gut, distended the flesh, and turned its victim rotten from the inside. Eventually even the Legion's primarch, Mortarion, became infected and in his delirium he called upon the Powers of Chaos to aid the Space Marines. Mortarion's fevered ravings were answered by Nurgle, and Mortarion became Nurgle's Champion.

The Death Guard, newly dedicated to Nurgle, arrived in time to take part in Horus's attack on Earth and took part in all of the major battles of the campaign. As disease began to disfigure the Death Guard, their appearance changed into the disgusting form they still bear today, and the once tall and noble Space Marines of the Death Guard became Plague Marines of Nurgle.

Of all the Chaos Space Marines, Plague Marines are the most physically horrible to look upon. Their flesh pulses with corruption, their innards spill through lesions in their putrid skin, and their bodies ooze with sticky slime. The sheer stench their rotting bodies exude fills the air around them with the sickly sweet scent of death for hundreds of yards in every direction. The sight of living creatures so foul is an abomination to nature, and of all the Plague Marines, those of the Death Guard are the most foul and disgusting, the most corpulent and corrupt.

Following Horus's defeat, Mortarion led his Death Guard in a merry dance of destruction over a score of planets until finally retreating with the remnants of the Legion into the Eye of Terror. Here he received Nurgle's ultimate reward and became a fully-fledged Daemon Prince ruling over one of Nurgle's greatest Plague Worlds in the Eye of Terror.

The Plague Planet Mortarion rules over lies deep inside the Eye of Terror. From this dark and slimy orb Mortarion launches fleets of plague ships into the warp to carry their contagions through the galaxy. On board are Champions of Chaos and their followers from the Plague Planet accompanied by warriors of the ancient Death Guard, the heinous Plague Marines of Nurgle.

The Plague Planet itself is a place where sickness and pestilence are the norm, where miasma clouds bring contagion and death and where the diseased pray to Nurgle for relief from their constant agony. Some of them are favoured and become Champions, and then fight among themselves for mastery and the chance to become daemon princes in their own right. The Plague Marines rarely interfere in battles between rising Champions. In fact they are not commonly seen by the world's inhabitants except during the time when new Champions are selected and enter the ranks of the Plague Marines. Most of their time is spent attending on Mortarion or carrying out his wishes, spreading new diseases and travelling to other worlds to carry Nurgle's plagues to new victims.