Blank (Psychic) - Silent Sisterhood: The most well-known example of the use of Blanks by the Imperium of Man was the existence of the mysterious all-female order of Witch Hunters known as the Sisters of Silence.During the Great Crusade era in the late 30th and early 31st Millennium, their purpose was to hunt and kill rogue Human psykers whose activities presented a terrible danger to the people of the newborn Imperium.Also known as the "Silent Sisterhood" and the "Witchseekers," they were the militant arm of the Astra Telepathica and were referred to internally within the records of the Council of Terra (predecessor to the Adeptus Terra and the Senatorum Imperialis) as the Departmento Investigates.Along with the Legio Custodes, the Sisters of Silence had the right and duty to walk freely within the inner sanctum of the Imperial Vaults, the sovereign and sole domain of the Emperor and His Household at the behest and license of the Master of Mankind.The Sisters of Silence's primary base of operations was the Somnus Citadel on Luna, the moon of Terra. These warrior-investigators were tasked with the apprehension of untrained psykers, often colloquially referred to on primitive Human worlds as "witches," whose abilities sometimes manifested in ways that could be very dangerous to their fellow Human beings, particularly if they became possessed hosts for the foul entities of the Warp.The Sisters operated the Astra Telepathica's infamous Black Ships, which ranged the galaxy following behind the Great Crusade's expeditionary fleets in search of rogue psykers to capture or expunge, seeking to collect and carry them back to Terra where they would be tested and their eventual fate decided. Though few in number, the Sisters of Silence commanded great respect within the Imperium and most servants of the Emperor regarded them with some awe.Few would willingly stand in their way or interfere with their activities and few indeed were those who were comfortable in their presence. It is hardly surprising that Blanks are often treated like outcasts or lepers in Imperial society, rejected by their parents and banished from their homeworld's local settlements.Local superstitions on many worlds often warn about touching them, saying that to do so would bring bad luck. Resigned to their fate, many Blanks lead simple, solitary existences, as far away from heavily populated areas as possible.Following the end of the Horus Heresy, Mankind had become superstitious and fearful of the unknown, and the Silent Sisterhood were cast out by a distrustful Imperium.They disappeared from Imperial history for nearly 1,500 years, until the Imperium faced annihilation at the hands of the massive Ork WAAAGH! led by the Warboss known only as The Beast. The last vestiges of the Silent Sisterhood would play a key role in defeating this Ork WAAAGH!, thus diverting disaster.Though officially disbanded after the Age of Apostasy in the 36th Millennium, many enclaves of the Silent Sisterhood still fight for the Imperial cause in the modern era, albeit in a more secretive and specialist capacity than before, and would eventually play an important role against Abaddon the Despoiler and the forces of Chaos during the closing years of the 41st Millennium.Following the resurrection of the Primarch Roboute Guilliman during the 13th Black Crusade, the Sisters of Silence were reinstated formally as the Adeptus Astra Telepathica's Departmento Investigates and accompanied Guilliman on his Indomitus Crusade.