Aurelia was an Imperial Hive World that served as the capital planet of Sub-sector Aurelia in the Korianis Sector, and was also the original Chapter Planet of the Blood Ravens Space Marine Chapter. The Blood Ravens maintained their fortress-monastery at Selenon, within view of the hive city of the same name. It was a technologically advanced and profitable world that served as the economic heart of the region, and the proud namesake of the entire sub-sector.
In the late 40th Millennium, however, a Warp Storm engulfed the planet, summoned by the Great Unclean One Ulkair in his battle against the Blood Ravens. The Blood Ravens' Chapter Master Moriah and Librarian Azariah Kyras sealed the Greater Daemon within the heart of the planet, but the damage was done. Aurelia disappeared into the Warp, and remained there for almost a standard millenium, transformed into a perpetually-shifting Ice World devoid of all life save for daemons and other Warp entities. With the loss of Aurelia, the Blood Ravens were transformed into a fleet-based Chapter who recruited their Aspirants from the other worlds in the Aurelian Sub-sector. In the late 41st Millennium, Aurelia emerged back into realspace at the behest of the Forces of Chaos led by the Chaos Lord Araghast and the former Dark Apostle Eliphas of the Black Legion who wished to free Ulkair and wreak havoc on the Aurelia Sub-sector with the powerful daemon's aid. Through the efforts of the Blood Ravens' 3rd and 5th Companies during the conflict later known to the Chapter as the Second Aurelian Crusade, Ulkair was banished back to his prison and the Black Legion was thwarted.
From that time on, the Imperial Guard stationed a number of regiments to keep watch on the frigid planet, at least one of which later fell under the thrall of Ulkair.