Icon of the Sisters of Silence
The Somnus Citadel was a great Imperial fortress established on Luna, the moon of Terra, that served as the headquarters of the order of psychic Nulls known as the Sisters of Silence during the Great Crusade and Horus Heresy. It contained launch bays for the Black Ships of the Divisio Astra Telepathica that carried out the Great Tithe of Human psykers for the Imperium and was an impressive citadel set amidst the vaccuum of the lunar surface armed with automated gun-drones. In addition, parts of the citadel could be separated from its exterior portion and lowered into the lunar underground in case of attack.
During the early days of the Horus Heresy, the survivors of the Death Guard Legion frigate Eisenstein who had fled Horus' betrayal at the Battle of Isstvan III, including Battle-Captain Nathaniel Garro, the Remembrancer Euphrati Keeler and the Loyalist Death Guard Space Marines later known as "The Seventy" were interred within the Somnus Citadel on the orders of Primarch Rogal Dorn in his capacity as the Praetorian of Terra while he determined whether their story of horror in the Isstvan System was true.
A terrible battle erupted within the citadel when the mortally-ill Eisenstein Death Guard survivor Solun Decius, who had been infected with an unnatural, Empyrean-spawned disease through contact with the first known Plague Marines during an assault on the frigate, gave himself over to Nurgle to end his suffering, and allowed himself to be possessed by a Nurglish Daemon known as the Lord of Flies. Decius immediately mutated into a Nurglite abomination that resembled a humanoid fly and the Daemon slew numerous Sisters of Silence and the Loyalist Death Guard until he was killed by Nathaniel Garro.
After the incident, the Somnus Citadel was used as the base of operations for the Imperial Regent Malcador the Sigillite's newly formed covert group of Space Marine agents known as the Knights-Errant that were commanded by Garro as the Sigillite's Agentia Primus.
Shortly before the Siege of Terra began, the Sisters of Silence abandoned the Somnus Citadel in order to help fortify the Imperial Palace instead. It was subsequently said to be ruined and abandoned in the wake of the Traitor Legions' assault on Luna, but apparently a group of Sisters of Silence known as the "Fellowship" remained for long millennia afterwards. At the dawn of the Indomitus Crusade in the Era Indomitus in the 41st Millennium, on the orders of the recently resurrected Primarch Roboute Guilliman, the Somnus Citadel was restored to serve as the headquarters of the revivified Silent Sisterhood.
Sources[]
- The Flight of the Eisenstein (Novel) by James Swallow, Ch. 15
- The Buried Dagger (Novel) by James Swallow, Ch. 2
- Watchers of the Throne: The Regent's Shadow (Novel) by Chris Wraight, Ch. 6