The Pit of Raukos was an anomaly set apart from the main storm front of the Great Rift which divided the Imperium in two. It was an isolated wound, but a deep one. It punched a hole through space time and ran far into the heart of the warp. It was an area of bruised void millions of kilometres across, glowing a sickly purple. Towards the middle, its colouration tended to putrid yellow-white, and at the very centre a vast, dark orb – striated like the iris of an eye – rotated with the speed and ferocity of a pulsar.

At the edge of this blot on reality languished a star system. It had never been settled or given a name by mankind, but bore the Adeptus Astra designation of 108/Beta-Kalapus-9. The sun was a medium red star dwarfed by the Pit. Gravitic shear drew long plumes of incandescent gas from the star towards the anomaly. In the years since the Great Rift had opened, the sun had shrunk by a tenth. The planets that orbited it were going dark.

Tendrils of glowing matter twisted out from the fringes of the spinning eye, merging with and bending the surrounding star gas into looping whorls that reached towards the greater slash of the Cicatrix Maledictum like parasitic worms migrating from their host.

Such breaches between dimensions were once terrifying anomalies. In these dark times, they had become commonplace. Whereas before there had been the Eye of Terror and the lesser Maelstrom, now the Great Rift split the galaxy side to side, its depths interfacing directly with the immaterium, and a thousand places like the Pit of Raukos pierced the flesh of reality, disgorging unnatural energies.

The Pit was named after a daemon prince Guilliman had slain. From its churning depths came unnatural plagues and fleets of half-mad sentient vessels crewed by children’s nightmares. Ghostly armies of impossible monsters spilled gibbering into realspace. Things spawned by the collective horrors of all history’s thinking beings emerged from dark corners on worlds for light years around it. Most of these things only had a brief foothold in reality, and the more esoteric types dissipated as soon as they were birthed, smeared to glowing corposant by the laws of material physics. But nature’s iron grip had loosened. The Pit of Raukos was an open gate to the daemonic legions of the greater powers. Empowered by the wills of their Dark Gods, and sustained by the unnatural energies of the rift, armies of fell entities emerged from Raukos. The terror they generated fed them further, and so the cycle of horror continued.

Guilliman stared unflinchingly into the unclean cyst of the Pit.