During the Great Crusade and Horus Heresy eras in the late 30th and early 31st Millennia, the Adeptus Astra Telepathica possessed a militant arm which was referred to internally within the records of the Adeptus Terra as the Departmento Investigates. But they were known throughout the galaxy as the Sisters of Silence, the Silent Sisterhood and the Witchseekers. The Silent Sisterhood was an all-female Imperial order of Witch Hunters dedicated to the elimination of psychic threats to Mankind. Their primary base of operations was the Somnus Citadel on Luna, the moon of Terra. Their purpose was to hunt and kill rogue human psykers whose activities presented a terrible danger to the people of the newborn Imperium of Man. The Sisters of Silence were well-trained warriors, and with the added bene