Cadia was a fortress world of immense strategic importance, standing sentinel at the mouth of the Cadian Gate, the most stable passage between the Eye of Terror and the wider galaxy. For thousands of years it served as the Imperium's foremost bulwark against the forces of Chaos, and its fall would mark one of the darkest turning points in recent history.
The planet bred some of the finest soldiers the Astra Militarum has ever fielded. Cadian regiments were renowned for their discipline, marksmanship, and unshakable resolve, trained from childhood amid a world bristling with defensive fortifications and haunted by the ever-present threat of invasion. Ancient pylons of mysterious origin dotted its surface, structures that helped hold back the warp's corrupting influence and kept the region navigable.
During a climactic assault led by the arch-traitor at the head of a massive Black Crusade, Cadia was besieged and ultimately broken, its surface shattered in a catastrophe that saw the world itself destroyed. Its destruction weakened the barriers restraining the warp and contributed to the tearing open of the Great Rift. Though the planet is gone, the defiance of its people endures as a rallying cry: Cadia stands, even when Cadia has fallen.