The Sigillite
The Sigillite is a division within the Imperium that is responsible for archaeological expeditions to recover both alien and ancient DAOT artifacts. They also had the added duty of combating the threats represented by such relics. It is known to the Imperium that amongst the greatest of powers came not from weapons or armies, but rather from the remnants of Dark Age of Technology. Thus, the Sigillite was charged originally with seeking out legendary lost DAOT artifacts. In time, its mission expanded to include any ancient object that is either technological or Psychical from any culture so long as it is not tainted by Chaos. Upon its formation, it was technically a part of the Imperial Military and comprised of a mixed group of scholars, Magos Explorators and archaeologists that worked alongside experienced officers that are trained in history. However, Later it became a separate Organization altogether.
The branch worked on Imperial-controlled worlds particularly that Fall under 11th Legion's Domain where they dedicated resources and used its authority to oversee massive excavations if evidence suggested that valuable artifacts were going to be unearthed. On neutral or even Non-Imperial worlds, they relied on more covert means of claiming lost treasures before they fell into the hands of an enemy of the Imperium.
The Sigillite, was founded early on by 11th Primarch with Malcador's Blessings after Primarch discovered Ruins of Nalanda Library. Organized officially as the Archaeological and Research Division of Imperium was instrumental in the discovery of many of the galaxy's ancient, forgotten secrets as well as the mapping of several of the galaxy's Warp routes. While officially members of the Imperial Guard, Sigillite members exists outside of the normal class and rank structure that the Imperial Guard was attempting to establish early on.
While their Main base is located in Valhalla, the Sigillite Order created a fleet of ships that are outfitted to be space-faring repertories and academies. These academies are used to train those Initiates in a different type of learning. These individuals were later assigned piloting or other roles aboard the ships or turned their talents to other duties. In addition to those ships, they maintain a fleet of scout, survey, and transport ships that were spread across the galaxy, from which it organized many systems and planetary mapping efforts, archaeological expeditions, and other missions of discovery. Aboard the larger vessels in the fleet, researchers examine the seemingly endless stream of data, records, and artifacts brought to them by their far-flung colleagues. It is these dedicated researchers who interpret historical data, translate ancient texts, and study mysterious artifacts in an attempt to make sense of both Human and galactic history at large.
"We have determined with 27.439% accuracy that the Xenos dwellings are built atop a human city, pre-dating the Age of Strife. The virus bombs are being consecrated as we speak. Cleansing can begin upon your order."----------- Magos Delphan Gruss of Sigillite Order
Aside from the Main fleet and exploration ships, the Sigillite maintained shipyards and research facilities on most of military outpost within the Imperium. From here, non-Sigillite could join up with the fleet to spend time among the stars and learn about the mission of the Sigillite. Because of their close association with the Magos Explorators, the Sigillite even have a facility located on Mars. In addition, they worked with the Malcador's Agents. Due to the nature of its missions, Sigillite is composed primarily of Magos Explorators, archaeologists, Navigators, with a few Military personal mixed in. Of the different classes that made up the Sigillite membership, Navigators and Military Personal are less important than actual archaeologists in Field.
Because they wander deep into uncharted territory, the members of this branch saw the most combat out of all the Imperial Navy. As members' missions often take them into the wild parts of the galaxy and expose them to a tremendous danger on a regular basis, they had a reputation as the hardiest, most courageous, and most battle-hardened members of the Exploration Fleet. This reputation attracts Scholars from across the Imperium who have a taste for adventure or who desired to hone their skills in combat and survival.