The Apostasy Gambit
The Imperial Navy is one of the armed forces of the Imperium of Man. While the Imperial Guard represents the Imperium’s ground forces, the Imperial Navy is responsible for the fleets of starships that maintain order between the stars and planets in the Imperium, for all space and air support provided to the infantry of the Imperial Guard, and for transporting those Guardsmen across the galaxy to the Imperium’s myriad warzones. The battlefleets of the Imperial Navy are constantly engaging threats both inside and outside the Imperium’s borders.
The Imperium is divided into five fleet zones known as the Segmentae Majoris. Every starship of the Imperial Navy is assigned to one of these Segmentae, and falls under the command of the respective Lord High-Admiral who commands all the Imperial Navy assets of that Segmentum. The naval assets of an entire Segmentum are named after that division of the Imperium; i.e. all of the Imperial fleet assets in the Segmentum Solar are known as the Battlefleet Solar, all the assets in the Ultima Segmentum are the Battlefleet Ultima, and so on. There are five Lord High Admirals, one controlling the assembled Battlefleet of each Segmentae. Although all 5 High Admirals are ranked equally, command of the Segmentum Solar is considered the oldest and therefore the most prestigious and senior posting. It is not uncommon for one of these Lord High Admirals to sit on the Senatorum Imperialis as a ruling High Lord of Terra. All Imperial shipping, civilian or military, is supervised within the jurisdiction of one of the five Segmentae. Each Segmentum has an orbital headquarters called a Segmentum Fortress which forms the base of fleet operations within the Segmentum. The Segmentum Fortress is controlled directly by a high-ranking official of the Adeptus Administratum known as the Master of the Segmentum, who reports only to the Master of the Administratum.
Battlefleet Calixis is a colossal fleet of Imperial Navy vessels charged with the the protection of the Calixis Sector, an Imperial sector located in the Segmentum Obscurus on the northern edge of the known galaxy, near the Halo Stars and the Eye of Terror. To the trailing edge of the galaxy, the Calixis Sector is bordered by the hazardous territories of the Fydae Great Cloud and to spinward by the Scarus Sector.
Battlefleet Calixis origins can be traced back to 384.M39, when the Calyx Expanse was officially declared conquered and the Angevin Crusade at an end by General Drusus. The sector’s Imperial Navy headquarters is located at the orbital void-station known as Port Wrath within the Golgenna Reach Sub-sector. The ships of Battlefleet Calixis are widely dispersed across the sector; some maintain the trade routes and well-travelled courses of the great chartist vessels, while others patrol the danger zones of the Adrantis Nebula and the Hazeroth Abyss where dark forces lurk still. But their most unpredictable and dangerous task is to guard the border of the Halo Stars, beyond which horrors uncounted and unknown lurk beyond the reach of Imperial space.