The Sanctum is the fortress-monastery of the Knights of Altair space marine chapter. An asteroid orbiting in deep space, the Sactum’s location is one of the most protected secrets of the chapter.

A fortress-monastery is the headquarters and spiritual home of a Space Marine Chapter.

Among those chapters who claim a world as their own, such as the Space Wolves, their fortress-monasteries often are built on the tallest mountain peaks of their planet—or in some isolated and inhospitable locale, such as a radiation-soaked desert or death-world jungle

For space-based chapters, their largest Battle Barge or an ancient star fortress may serve as home.

The history of the Knights of Altair has led them to a rather unique citadel. Their fortress-monastery encompasses a 20-kilometer-in-diameter asteroid in deep space.

Ancient History

The home of the Knights of Altair has always been a mystery. For reasons explained elsewhere, the Knights of Altair spent unrecorded decades—perhaps centuries—guarding the forge world of Helios. A small fortress-monastery was built on the planet, and it remains there yet, but the time came when the chapter was freed from its garrison duties and was ready to take on a greater role in the defense of the entire Corvus Cluster.

For that, it needed a larger and more robust headquarters. It is said that, in the early 38th Millennium, the Fabricator-General of Helios deeded to the Knights ownership of a sizable asteroid that orbited Helios at half-a-light year distance—close enough to respond to the defense of Helios yet far enough way that it would remain unnoticed by any hostile fleet that stumbled across the secretive forge world.

Here was what the Knights of Altair sought: a citadel, a refuge, a home. They named it The Sanctum.

A Citadel in Space

Massive macro-cannon turrets dot the surface of the Sanctum.

It will come as no surprise that the entire asteroid has been converted into an armed fortress. Every kilometer of its surface is bristling with macro-cannon turrets, heavy bolter bunkers, and missile batteries that constantly scan the star-lit sky for foes, ready to unleash their deadly firepower at a moment’s notice.

The interior of the Sanctum  is equally formidable in its defenses. The tunnels and passageways beneath the surface are designed as a maze to confound invaders that seek entry.  And, every few hundred meters, an enemy will be confronted by thick plasteel gates, ferrocrete bunkers, deadly gun emplacements, and even chambers lined with explosive charges.

One cunning novelty to this design is that there are hundreds of shifting wall sections, which can close off a passageway, funnel an enemy into the path of gun emplacements, or  leave an invader moving in circles.

The most critical areas of the fortress-monastery also are difficult to reach, as the greater their importance, the deeper they are buried into the asteroid. For example, the Great Hall of Dorn, the spiritual heart of the chapter, is located nearly four kilometers below the surface. The Apothecarion, where the chapter’s precious gene-seed is stored, lies at the very center of the asteroid.

All these defenses are bolstered by the Sanctum Auxilia, a 50,000-man garrison drawn from the serf population that inhabits the asteroid. They are well-trained, well-armed, and highly motivated.

The end of a 300-meter-long hydroponic garden, one of thousands that run beneath the surface of the asteroid. Still, although the chapter puts significant resources into its underground agricultural efforts, the Sanctum still needs to import food.

Inhabitants

In addition to the chapter’s warriors, approximately 300,000 base-normal humans and servitors inhabit the Sanctum. Excepting some specialists recruited from other worlds, all inhabitants were born and raised on the asteroid, and—for security reasons—they and their descendants will live out their lives within its confines.

The vast majority of the population are chapter serfs. They tend to the hydroponic gardens that produce food, clean, cook, and perform other basic duties on behalf of the chapter. A smaller percentage of inhabitants are tech-servants who maintain the basic infrastructure of the fortress-monastery under the careful eye of a cadre of Mechanicus personnel who maintain its weapons, equipment, power plant, medical facilities, and other critical facilities.

Following the example of the Ultramarines, the Knights treat their servants with more respect and kindness than many other space marine chapters. Even serfs are granted certain freedoms, are allowed time for personal and family interests, and cannot be arbitrarily disciplined by an Astartes warrior.

Still, all inhabitants are expected to display the utmost respect to a Chapter warrior, and there are 112 unbreakable rules that serfs must obey—87 of which entail severe physical punishment, and 27 that are capital offenses.

The Armory

A strong bond exists between Helios and the Knights of Altair, and the Sanctum has benefited greatly from this relationship. The fortress-monastery boasts a massive armory  equipped with the most technologically advanced forges and manufactorums and dedicated to the production of weapons, ammunition, and vehicles.

This facility is one of the most protected areas of the fortress-monastery, encased behind half-a-kilometer of rock, and with the added protection of walls of adamantium, ferrocrete, plasteel, and null shields. Thick blast doors, coated with reactive defensive armor, guard all entrances, and access is limited to those with the proper gene-print and coded signal.

Given the challenges of resupply in the depths of space, the armory has stored an immense stockpile of weapons and ammunition for its Astartes warriors. Dozens of massive ammo silos exist, each stacked 50 meters tall with ammo, and with bolter guns, plasma weapons, flamethrowers, and other weapons lined up in gun racks along the walls.

What’s more, as the surface area of the Sanctum is more than 1,200 square kilometers, even larger ammo storage units exist to supply the thousands of gun emplacements on the surface, and a vast network of shell-hoists and ammo-conveyors exist to ensure ammunition never runs in short supply during a battle.

Overseeing this impressive operation is the chapter’s master of the forge, Guiot Odinet, whose technological expertise rivals that of any techmarine in the Imperium. His work is supported by a number of other techmarines, as well several hundred tech-priests who are determined to ensure the chapter’s military capacity is as formidable as possible.

Click here to read Part 2 of this article.

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The Corvus Cluster is a Warhammer 40K blog documenting our gaming adventures in the fantastical sci-fi universe of Games Workshop.