Event · M42

Plague Wars

The Plague Wars were a Death Guard invasion of Ultramar in the early 42nd millennium, led by Mortarion against his brother Roboute Guilliman. Imperial records place the conflict’s decisive phase around the twelfth year after the launch of the Indomitus Crusade, with fighting spreading across many of Ultramar’s Five Hundred Worlds, among them Espandor, Parmenio, and the shrine world of Iax, where the invasion was ultimately broken. The war’s roots lay in the systems to Ultramar’s galactic north, later known as the Scourge Stars, where cults loyal to the Chaos god Nurgle spread plague among once-prosperous Imperial worlds even before the Great Rift tore open the galaxy. The onset of the Noctis Aeterna, the darkening of the Astronomican that followed the Rift’s birth, gave Mortarion cover to turn these captured systems into a staging ground for a full invasion of Ultramar, a realm he had long resented as the domain of the brother who had once turned him from a life of service to tyrants. Mortarion did not move alone: the First Captain Typhus, once known as Calas Typhon before his fall to Nurgle, led a plague-ridden armada against Ultramar’s outer star forts and shipping lanes, while the Great Unclean One Ku’gath Plaguefather brought a daemonic host to the garden world of Iax to breed fresh contagions there. Unable to storm Macragge directly, Mortarion instead battered Ultramar’s lesser worlds to draw Guilliman into open battle, besieging Espandor and Ardium while Typhus’s fleet destroyed several of Ultramar’s watching star forts. Guilliman, newly returned to Ultramar after leading the first phase of the Indomitus Crusade, liberated Ardium and destroyed a Plague Engine built around the relic known as the Hand of Darkness, which had been raising the slain as plague zombies. When Mortarion struck at the Konor system to sever Guilliman’s route back to Macragge, Imperial forces held all three of its core worlds, and the corrupted death world of Loebos, Mortarion’s intended foothold, was destroyed in the fighting. Guilliman then launched the Spear of Espandor, a counter-offensive that broke the siege of Espandor, cut Mortarion’s forces off from the Scourge Stars, and saw Guilliman slay the Great Unclean One Qaramar in single combat. The war’s largest armoured and Titan engagement followed on Parmenio, where Guilliman was nearly killed in an ambush sprung jointly by Mortarion and Ku’gath before being saved by a warrior likened to a Living Saint. The final battle came on Iax, where Mortarion and Ku’gath sought to destroy Guilliman with a contagion known as the Godblight, even as the opening of a wider war in the Great Rift drew away much of Nurgle’s daemonic strength. Amid Iax’s ruined shrines the two primarch brothers are recorded as having fought directly, a confrontation that later tradition treats as one of the era’s defining single combats. Denied the annihilation he sought, Mortarion withdrew his surviving forces to the Scourge Stars under cover of a virus-bomb strike, leaving Ultramar scarred by plague and war but unconquered. The Plague Wars are remembered as the trial that followed the first phase of Guilliman’s Indomitus Crusade and preceded the further campaigns that drew him back out across the Imperium, while for Mortarion the failure only deepened the enmity that continued to shape his dealings with the Ultramarines. Typhus commanded the Plague Fleet, separate from Mortarion’s host and from Ku’Gath’s, and led a splinter fleet through the outer regions of Ultramar. He is recorded in the attempt on Roboute Guilliman during the fighting on Parmenio. He is not recorded on Iax. After the battle on Parmenio, Nurgle ordered a withdrawal to the Scourge Stars. Typhus left with a large part of the Death Guard. Mortarion, who wished to remain and use the Godblight, stayed with Ku’Gath. During the Plague Wars Guilliman recalled Marneus Calgar to Ultramar. Calgar put down risings of the Ultramar Auxilia in the Illyrian region of Macragge and attended the conclave at the Fortress of Hera at which Guilliman restored the Tetrarchy and said that Calgar would preside over it. He is not recorded as taking the field against the Death Guard on Espandor, Parmenio, or Iax. Chief Librarian Varro Tigurius, recovered from the coma into which the birth of the Great Rift had cast him, oversaw the quarantine of the Library of Ptolemy and much of the defence of Macragge during the war. When the Great Unclean One Rotigus manifested inside the Library before the remembrancer Fabian Guelphrain, tempting him with a tome recording the history of Imperium Secundus, Tigurius intervened and fought the daemon briefly before it withdrew. On Espandor he was among the Librarians accompanying Guilliman, and after the Primarch struck Qaramar down with the Sword of the Emperor, Tigurius and those Librarians banished the daemon back to the Warp, ending the last major threat to Espandor’s reconquest. Captain Cato Sicarius, by then commander of Guilliman’s Victrix Guard, was among the forces the Primarch brought with him to Ultramar’s aid. He was present at the conclave in the Fortress of Hera at which Guilliman announced the changes he was making to the governance of Ultramar.

See where Plague Wars occurred on the galactic map in the 41st Millennium.

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