The First War for Armageddon

The First War for Armageddon was a daemonic invasion so terrible in its nature that the Imperium ultimately chose to erase the very memory of it. From the churning warp there descended Angron, the daemon primarch of the World Eaters, leading a vast host of bloodletting daemons of Khorne against the sprawling hive world of Armageddon in a tide of slaughter meant to raise a monument of skulls to the glory of the Blood God.

The planet's mortal defenders were swiftly overwhelmed as a murderous madness spread unchecked among the population and daemons walked openly through the burning hives. Into this unfolding nightmare came the Grey Knights, the secret and mysterious Chaos-hunting Chapter, fighting shoulder to shoulder with the Space Wolves to stem a supernatural horror that ordinary Imperial armies could not even comprehend, let alone hope to withstand. Towering Titans of the Adeptus Mechanicus strode into the burning hives to hold the line, yet even they were sorely tested by the relentless daemon host.

The war reached its climax when the Grey Knights at last confronted Angron himself upon the field. At ruinous and staggering cost to their own secretive brotherhood, they contrived through sorcery and sacrifice to banish the raging daemon primarch back into the warp before the anchoring of his invasion into reality could be fully completed, breaking the incursion at the price of hundreds of their own irreplaceable lives.

Yet victory came wrapped in bitter shame. To keep the very existence of daemons a secret from the mortal defenders who had witnessed them firsthand, thousands of surviving Space Wolves and Imperial Guardsmen were quietly purged or exiled, their heroism rewarded only with silence and death. The war is set within the account of the Grey Knights.