The Forbidden Fortress is the Adeptus Astronomica’s hidden base on Terra, built inside the Himalazia mountains. It houses the Astronomican, the psychic beacon that guides Imperial ships through the Warp, making it one of the most vital sites in the Imperium.
What is the Forbidden Fortress?
The Forbidden Fortress is also called the Fortress of the Astronomican or the Hollow Mountain. It’s the headquarters of the Adeptus Astronomica and contains the Chamber of the Astronomican, the huge spherical chamber where the Astronomican itself operates.
The Emperor built it at some unspecified point in the Imperium’s distant past. From the outside, the mountains look untouched, but the Fortress extends deep into the rock and runs throughout the entire range.
The Astronomican and its cost
The Astronomican is a psychic beacon that lets Imperial ships navigate the Warp. Powering it requires a daily sacrifice: a thousand psykers are fed to the Golden Throne to keep the light burning.
Not everyone sent to the Fortress is doomed right away. Powerful psykers like Space Marine Librarians or Imperial Guard Sanctioned Psykers are chosen to wear black robes and serve there. Eventually, they too are sacrificed.
Layout and defenses
The Chamber of the Astronomican is a massive sphere inside a single mountain. The mountain’s peak is sculpted to form the upper half of the sphere.
Vast city-sized emitters surround the Fortress, transmitting the Astronomican’s power across the Imperium. Together they’re about the size of the Imperial Palace. Tech-Priests of the Mechanicum maintain this ancient, degrading technology, and its power conduits run all the way back to the Golden Throne.
Impossibly huge cables link the Fortress to the Palace along a trench hundreds of kilometers deep. That trench is lined with Mechanicum equipment, gun batteries, and Void Shield arrays.
Grey-clad guardians of the Adeptus Astronomica protect the Fortress. They wear Carapace Armour and carry Lasguns. Uninvited access isn’t allowed, even the Adeptus Arbites and the Inquisition must ask permission first.
The Fortress during the Noctis Aeterna
During the Noctis Aeterna and the daemonic incursion on Terra, the Forbidden Fortress was assailed by the Warp. Its adepts went mad, and many became possessed by Daemons.
Inquisitor Erasmus Crowl and his retinue arrived to find one of the Imperium’s most vital sites in total disarray. Imperial Fists reinforcements showed up soon after and scoured the complex of its daemonic infestation.
Key facts
- The Forbidden Fortress is also known as the Fortress of the Astronomican or the Hollow Mountain.
- It’s the base of the Adeptus Astronomica and houses the Astronomican.
- Built by the Emperor in the Himalazia mountains on Terra.
- A thousand psykers are sacrificed daily to power the Astronomican.
- Protected by grey-clad guardians with Carapace Armour and Lasguns.
- During the Noctis Aeterna, it was attacked by daemons and later cleansed by the Imperial Fists.
FAQ
Where is the Forbidden Fortress located?
It’s on Terra, built within the Himalazia mountain range. The mountains look unchanged from the outside, but the Fortress extends deep underground and throughout the range.
What is the Astronomican?
The Astronomican is a psychic beacon powered by the sacrifice of a thousand psykers each day. It guides Imperial ships through the Warp.
Can anyone visit the Forbidden Fortress?
No. Even the Adeptus Arbites and the Inquisition need permission to enter. It’s protected by grey-clad guardians of the Adeptus Astronomica.