Hive Tertium - Reign of House Margrave to the 41st Millennium: In the 36th Millennium the expansion of the cluster of three hive cities led by House Barquette and its alliance of noble houses continued. Over the Terran centuries, the population of the hive cluster of three cities under House Barquette's control grew exponentially and the arcologies' vital systems soon become interlinked, leading to the emergence of a single, massive hive city that now covers an extensive portion of Atoma Prime's surface. The unified arcology is named "Hive Tertium."Consequently, any remaining populations outside of the hive city now merge and Hive Tertium becomes the primary and perhaps only population centre on the planet. The rivalry between House Barquette and other Highborn houses continues and intensifies within the higest spires of Tertium.At some point in the 36th Millennium the upstart House Margrave launches a coup with allies of its own and replaces House Barquette as the ruling house of Atoma Prime and the Moebian Domain following yet another period of instability. Anselm Margrave is declared the new Lord Moebian in the wake of the coup. It is also at this time that the world known as Mornax is recorded as having been brought into the Moebian Domain as a vassal world.Over the next few thousand years the Moebian Domain enjoyed a period of stability and calm. There are no extant records of any major incidents or conflicts, nor does the xenos Fringe War appear to have flared up once more.In the 38th Millennium, the worlds of Mornax and Branx Magna were officially granted membership within the Moebian Domain. In the late 39th Millennium, the Ocean World of Incron was reclaimed and also became part of the domain. The Navis Imperialis sector battlefleet depot above Atoma Prime was relocated to Incron for unknown reasons at this time. In the early 41st Millennium, the world of Pavane was charted and claimed as part of the domain.By the 41st Millennium the Moebian Domain and Atoma Prime seemed a stable and well-managed region of the Imperium. There had been steady economic and population growth over the preceding six millennia and the Moebian Domain now comprised seven main worlds, the capital Atoma Prime with its massive hive city of Tertium, Crucis which had been designated as a Shrine World of the Ecclesiarchy, and then five other worlds including Incron, Rocyria, Branx Magna, Pavane, and Mournax. The domain also maintained several vassal worlds, the most notable being Infidus Brim. Branx Magna had expanded its industrial output and population to a level that it now rivalled even Atoma Prime in terms of its gross planetary product and industrial importance within the star system. Its planetary governors belonged to a noble dynasty known as House van Spasie.On Atoma Prime itself, Constant Margrave was the Lord Moebian, the 13th head of House Margrave to hold the office and rule the Moebian Domain. Lady Margrave, his sister, while officially subservient to her brother, also held some measure of power within the domain. Unfortunately, the Fringe Wars against the Darktide had flared up once more with increasing regularity.A specific world was noted to be the site of one of the on-going conflicts in the Fringe War at this time. This was the planet of Nox Alpha, a world that was not part of the Moebian Domain as either a member or a vassal world, but possessed an inherent strategic value for the Imperial forces fighting on the Fringe.