The Plague Wars were a brutal series of battles in the Realm of Ultramar, where the forces of Nurgle tried to claim the prosperous worlds for the Plague God’s Garden. They pitted the returned Primarch Roboute Guilliman against his daemon brother Mortarion, and they reshaped the eastern Imperium in the era after the Great Rift.
How the plague wars began
Nurgle’s interest in Ultramar started before the Great Rift tore the galaxy open. The Plague God quietly spread Cults of Corruption and a host of diseases through three Imperial systems to the galactic north of Ultramar, which later became known as the Scourge Stars.
Those systems turned into a launchpad. When the Great Rift appeared during the Thirteenth Black Crusade, Nurgle decided the time was right to fully commit, and the Death Guard invaded Ultramar in force.
The invasion and Guilliman’s counterattack
Mortarion led the main Death Guard fleet himself, while Typhus commanded the Plague Fleet and the Great Unclean One Ku’Gath brought a daemonic host that ravaged the Tartella System. Their goal was simple: drown Ultramar in pestilence and add it to Nurgle’s Garden.
Roboute Guilliman, recently returned and leading the Indomitus Crusade, couldn’t let that happen. He rallied the Ultramarines, Ultramar’s tetrarchs, and allied forces to push the invaders back. The fighting was savage and spread across multiple worlds.
Key battles and the duel on Iax
The war saw major actions on Konor, Iax, Parmenio, and other Ultramar worlds. On Iax, Guilliman and Mortarion finally clashed in person, a duel that became the symbolic heart of the conflict.
The battle on Iax ended with Mortarion banished back to the Warp, though not without cost. The Imperium won overall, but the Death Guard didn’t leave quietly. They withdrew to the Scourge Stars, and the war for that region kicked off almost immediately.
Aftermath and why it matters
The Plague Wars were a strategic win for the Imperium, but they left Ultramar scarred and proved that Nurgle’s reach extended far beyond a single daemon world. The Scourge Stars remain a festering threat on the Imperium’s doorstep.
For Guilliman, the war was personal. It forced him to confront his brother’s fall and the reality that Chaos isn’t just a distant enemy, it’s family. The conflict also set the stage for the later War for the Scourge Stars and the events of the Dark Imperium novels.
Key facts
- The Plague Wars were fought in Ultramar between the Imperium and Nurgle’s forces around 012.M42.
- Mortarion led the Death Guard invasion, supported by Typhus and the daemon Ku’Gath.
- Roboute Guilliman commanded the Imperial defence and personally duelled Mortarion on Iax.
- The war ended in an Imperial victory, with Mortarion banished and the Death Guard pushed back to the Scourge Stars.
- It marked a major test of Guilliman’s leadership after his return and deepened the feud with his fallen brother.
FAQ
Who fought in the Plague Wars?
The Imperium, led by Roboute Guilliman and the Ultramarines, fought against the forces of Nurgle, primarily the Death Guard under Mortarion, Typhus, and the Great Unclean One Ku’Gath.
When did the Plague Wars take place?
They occurred around 012.M42, at the end of the first phase of the Indomitus Crusade, after the Great Rift opened.
What was the outcome of the Plague Wars?
The Imperium won overall. Mortarion was banished, the Death Guard retreated, and Nurgle’s plan to absorb Ultramar failed, though it led directly into the War for the Scourge Stars.