The Destroyer Plague is a disease conjured by Nurgle, the Chaos God of Decay. It takes the form of warp-spawned flies that infest every orifice of the body and lay their eggs in their hapless victims. The victims' abdomens become bloated until they finally burst, unleashing another wave of plague flies to spread the contagion once more. The Destroyer is described as the most horrific and vile plague in Grandfather Nurgle's arsenal.
When Calas Typhon, First Captain of the Death Guard, led his Legion into the warp, the Legion was struck down by a curious paralyzing illness, a precursor of what was to come. Though Astartes are normally resistant to disease, against the power of Nurgle they had no defense. As the Destroyer spread throughout the Death Guard fleet, bursting the guts of the hardy Space Marines, Typhon - on the bridge of his flagship, Terminus Est - was the first to stir. He came uncertainly to his feet, and spoke only one phlegm-laced word: "More." With that word, the flies left their hosts broken and bloated, and entered Typhon's body like a wave. Surprisingly, he remained on his feet, but was now a hive of pestilence. He is now known as Typhus, Herald of Nurgle and host of the Destroyer Hive.
The first Plague Marines were members of the Death Guard during the Horus Heresy. Horus planned for the Death Guard to form part of the invasion force he would lead to attack Terra. Determined to join the Warmaster’s siege of the Imperial Palace, Mortarion led his fleet into the Warp. He did not know that he was entering an eternal nightmare from which he would never escape.
The fleet was trapped and becalmed in the midst of an impenetrable Warp storm. No one could guide the ships through the murk, and they were unable to shift the fleet back into realspace. Few knew this was truly a part of Calas Typhon’s plan. The entire fleet was forced to drift helplessly through the Immaterium. Without hope of salvation, their warships moved aimlessly. It was during this time that the infections of Nurgle began to silently assail the Death Guard. One by one, the Destroyer Plague and Nurgle’s Rot – two of the favoured inventions of the Plaguefather – infiltrated their ships. Had they been any other Legion, the Death Guard would have succumbed to the horrific maladies that beset them. Instead, the superhuman augmentations of the Space Marines proved their worst enemy; their own legendary resilience was rendered into a flaw for, despite the dire diseases which now polluted their every bodily function, they could not die. Instead, the Death Guard were slowly, sickeningly transformed.
Unable to endure the suffering any longer, Mortarion first offered into the Immaterium himself, followed by his Legion, and finally his very soul in exchange for deliverance. A presence in the Immaterium answered, as though it had been waiting all along, biding its time. In the depths of the Warp, the great god Nurgle, Lord of Decay and Father of Disease, claimed that debt and accepted Mortarion and the Death Guard as his own. Thus were born the first Plague Marines.
Eventually with the entire Death Guard fleet, Mortarion set off to Terra to join the siege. Unfortunately the fleet was caught in an impenetrable warp storm, the navigators not being able to find a way through the warp or a way back into real space. The fleet was reduced to drifting, and in that time the Destroyer came. The plague that came could not be resisted, something that terrified Mortarion and the Death Guard. It transformed them into bloated mutants, yet none could die, their own body being their undoing. None suffered more than Mortarion, for it was like being on the mountain top again, surrendering to the toxins, but this time without the Emperor to save him. Eventually, Mortarion could suffer no more and gave himself to Chaos. Father Nurgle responded and took the legion and Mortarion as his own.
