The Fall of Cadia

For ten thousand years the fortress world of Cadia stood sentinel at the mouth of hell, the keystone of the Imperium's defence against the daemon-haunted Eye of Terror. When Abaddon the Despoiler launched his Thirteenth Black Crusade in the final years of the 41st Millennium, that ancient vigil was tested as never before, and the war that followed would shatter Cadia utterly and split the galaxy in two.

The Gate of the Damned

Cadia guarded the Cadian Gate, the only reliably stable passage between the Eye of Terror and the wider galaxy. Whoever held it controlled the flow of daemon fleets and traitor armadas seeking to reach the heart of the Imperium, and so the world was fortified into a bristling bastion, its people raised from birth as soldiers. The Cadian Shock Troops of the Astra Militarum were counted among the finest human warriors in existence, and they had turned back the Despoiler many times before.

Across the planet's surface rose the Cadian Pylons, colossal black structures older than mankind's memory. Few understood their purpose, for they were relics of the Necrons, raised in a forgotten age to hold the tides of the Warp at bay. So long as the pylons endured, the boundary between reality and the Immaterium held firm around the Gate.

The Despoiler's Thirteenth Crusade

Twelve times before, Abaddon had led his Black Crusades out of the Eye, each a hammer-blow against the Imperium. The thirteenth eclipsed them all. Marshalling the largest host raised in service to the Dark Gods since the days of Horus, the Warmaster of the Chaos Space Marines fell upon the Cadian system with a fury that had waited ten millennia to be unleashed.

The void above Cadia became a graveyard of ships as the Imperial Navy fought to blunt the invasion. On the ground, orbital landings and daemonic incursions tore at the fortress lines. Yet the Cadians did not break. Reinforcements poured in from across the segmentum, and for a time the defenders held against the endless traitor assault.

Cadia Stands

The defence became legend even as it was fought. Regiments of the Space Marines, war-walkers of the Imperial Knights, the living saint Celestine and her Adepta Sororitas, and countless Guardsmen bled and died to hold the line. Their watchword rang across every vox-channel and every trembling trench: Cadia stands. It was a vow, a prayer, and an act of defiance flung into the face of Chaos itself.

But Abaddon had not come to conquer Cadia. Enraged by the world's endless resistance, and knowing the strategic prize it represented, the Despoiler resolved to end the defiance forever, no matter the cost to his own forces.

The Pylons and the Gamble

Unknown to most, a desperate hope had taken shape. The Archmagos Dominus Belisarius Cawl of the Adeptus Mechanicus, aided against all expectation by the ancient Necron collector Trazyn the Infinite, had at last unravelled the secret of the Cadian Pylons. Correctly aligned and awakened, the great structures might be used to seal the Eye of Terror shut, ending the threat of the Gate for all time.

It was a chance to win the war of ten thousand years in a single stroke. But the working demanded time the defenders did not have, and Abaddon, sensing the danger, chose to bring the whole edifice crashing down rather than risk his enemies snatching victory.

The World Broken

Above Cadia hung one of the Despoiler's Blackstone Fortresses, a moon-sized weapon of terrible age. Badly damaged in the fighting, the vast construct was steered by Abaddon on a final, deliberate course, plunging out of orbit to strike the planet like an artificial meteor. The impact obliterated much of Cadia's defence in an instant and shattered the network of pylons that had held the Warp at bay.

With the pylons gone and the world's crust tectonically ruptured, Cadia began to die. The Immaterium bled through the broken boundary, and within hours the fortress world tore itself apart. The survivors carried away a bitter truth that would haunt the Imperium forever: Cadia broke before the Guard did.

The Escape and the Great Rift

A handful of Imperial heroes escaped the dying world, spirited away through a hidden Webway gate with the aid of the newborn Aeldari faction known as the Ynnari. They fled a system consumed by fire, carrying warning of the catastrophe now unfolding across the stars.

For Cadia's fall did not end with Cadia. Unchained at last, the Eye of Terror swelled without limit, merging with lesser Warp storms until a galaxy-spanning wound tore across the heavens, the Great Rift. It severed the light of the Astronomican from half the Imperium, plunging countless worlds into isolation and darkness. The age that followed would be named the Dark Imperium, and it was born in the ashes of the world that swore it would always stand.