Seven Saints of Talis
Fort Novigaard was once a major military base operated by the Talisian PDF and, later, the forces of the Imperial Guard. It served as both a training ground and a staging point for combat operations across the planet, later housing infantry, armor and artillery regiments.
It survived the War of Seven Saints relatively unscathed, its long-range anti-aircraft batteries being able to destroy most of the inbound missiles, and forcing others off-course to impact the mountains to the north. It was, however, assaulted several times during the war and, though it never fell, suffered structural damage due to enemy fire.
Following the Night of Fire, the surviving soldiers held out for as long as they could, before rad-storms and the horrors of the Wasteland born of it forced them to withdraw. The base lay virtually unused (except by random, nomadic bands of survivors and, for a brief time, bandits) for several hundred years until its main doors were reopened by a band of roaming Tech-Priests.
What they found within was a marvelous collection of pre-war technology. Tanks, weapons, armor, and many more materials of war were safely stored within. Of much greater value, however, were the manufactorum facilities located in an underground vault, used by the Tech-Priests of old to manufacture arms for the Imperial Guard.
Thus, the Brotherhood of Steel was born.
Over the next two hundred years, the Brotherhood of Steel grew into a powerful faction of militant Tech-Priests. With Fort Novigaard once again operational, they fielded potent las-weapons and armored vehicles in their quest to plumb the depths of any Vault they could find. As time went on, this brought them into conflict with the Iron Priests of Thracia and the Children of the Atom of Pillarus Isle. Eventually, these three factions divided the Wastelands between them, with the Brotherhood of Steel taking the northern and western Reach, the Iron Priests taking Thracia, and the Children of the Atom taking Mount Pillarus and the southern Reach.
This came to an end in early 1077 when Fort Novigaard was assaulted by a potent Spyre Slayer. With primarily energy weapons to combat it, the Brotherhood of Steel simply could not deal significant damage to it, and, with the fortress being so very large, and surrounded on three sides by mountains, the Spire Slayer was able to stalk and slay many members of the Tech-Cult, until it had grown to sufficient power in order to rain deadly acids upon its foes. Once it had breached the inner walls, the Stalker simply hunted the survivors down, room by room, hall by hall, until only a handful of survivors remained of the Brotherhood of Steel, scattered to their various bunkers across the Wastelands.
Today, Fort Novigaard stands silent and ruined. The Spire Slayer has faded back into the Immaterium, leaving its war-chassis to rust and corrode in the rad-storms of the Wastelands. However, with the Brotherhood of Steel broken and scattered, the Orks of the Blackfang Hills have begun raiding southward. It is only a matter of time until the greenskins overcome the remaining automated defenses, and the surviving wargear of the fortress will be theirs.