Event · M30–M31
War in the Webway
The War in the Webway was a clandestine conflict waged by the Emperor of Mankind within the webway beneath the Imperial Palace on Terra during the Horus Heresy. It was fought in secret, hidden from all but a trusted few of the Emperor’s closest servants, and unknown even to most of the primarchs and the wider Imperium, who remained ignorant that their master was engaged upon two wars at once. The conflict arose from the Emperor’s labour on the Webway Project, an undertaking intended to open a stable, permanent gateway into the webway beneath the Palace and so grant Mankind safe passage through that ancient dimension without recourse to the warp. As he laboured upon this work, the Emperor was obliged to defend it in person against the predations of Chaos and other malign presences native to the webway, which sought to corrupt or breach the passage and so gain a path to Terra itself. The Adeptus Custodes and the Sisters of Silence stood guard over the physical approaches to the project, while the Emperor alone contested the deeper reaches of the webway. The war continued for as long as the Emperor could sustain it, but it was left unresolved when the opening of the Siege of Terra compelled him to turn his full attention to the defence of the Imperial Palace against the forces of Horus. The Webway Project was abandoned incomplete, and the toll taken upon the Emperor by his long, unseen struggle within the webway has since been reckoned by scholars among the burdens he bore into his final confrontation with the Warmaster.
See where War in the Webway occurred on the galactic map during the Horus Heresy.