Luna - Early Years and the Age of Strife: Luna is Terra's only natural satellite. Although not the largest natural satellite in the Segmentum Solar, it is the largest relative to the size of the planet that it orbits.Luna is in synchronous rotation with Terra, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters.Once, Terra's satellite had been a mottled stone wasteland where Humans had ventured in their first infantile steps away from their birth world in the late 2nd Millennium. They had built colonies there, testing their mettle in the pitiless cold of the void in preparation for future voyages to other planets, but as Terra's people had advanced, Luna had become little more than a way station, a place to pass by on the journey to the interplanetary -- and later, interstellar -- deeps.This age of exploration and advanced technology came to an end with the coming of Old Night, the chaotic and highly fragmented period of Human history between the 25th and 30th Millennia. By the end of the Age of Strife, Luna had become the bastion of a conglomeration of resurrectionist gene-cults known as the Selenar, whose members believed that Human nature was fractal, fractured and transcendent. To them, the true nature of Mankind was visible in the flesh and mind of the individual, but each person was an echo of archetypes that persisted throughout Human existence. Each Selenar gene-cult clung to a different set of archetypes: some represented them as anthropomorphic figures, some as numbers, and some as symbolic systems.Shot through with low occultism, most fell short of deification, but all pursued understanding through their craft of gene-forging. Each cult member was a product not of random breeding, but creation by the cult's gene-wrights according to formulae born in the Dark Age of Technology. Resurrected in body time and time again, they attempted to reach a true personification of a single Human archetype. In their subterranean complexes beneath the lunar regolith, the cults were powerful, insular and resistant to the Imperial Truth.Such resistance was hardly a novelty, and would normally have been dealt with in the usual manner -- by obliteration. The fact that the gene-cults had something that the growing Imperium needed complicated that position.Clouded as it might have been by occultism, the genetic engineering techniques of the Selenar Luna cults was unequalled save within the Emperor's own facilities on Terra. With Terra having completed its Unification by 798.M30, the conquest of the Sol System and the galaxy beyond beckoned.For the Great Crusade there would need to be a large number of Space Marines. The Terran gene-engineering facilities would not be able to cope with such a huge increase in the demand for the creation of recruits for the Space Marine Legions, so the newborn Imperium of Man needed Luna's wealth of gene-craft and technological capacity added to its own.But the Selenar gene-cults would not bow willingly to the hunger of the newborn Imperium, and had long fought off the machinations of Terran warlords and knowledge-hungry Martian magi in the past. The Selenar had previously received Imperial ambassadors with courtesy, but always answered their offers, threats and entreaties with silence.As the threats from Terra began to outnumber the offers, the Lunar cults started to turn away the ambassadors and gird themselves for the inevitable war to come. Normally highly factional, the possibility of Terran domination overcame all doctrinal disagreements between the Selenar cult matriarchs and gene-wrights -- they would resist the Imperium together and without limit.The final Imperial deputation to Luna was returned to Terra as a still-screaming soup of fused, liquescent flesh in the dead shell of their shuttle. So it was that the Emperor finally ordered Luna to be pacified by the sword, their superstitious beliefs cast down before the Imperial Truth and their gene-craft yoked to the needs of the Imperium.As such, Luna would become the site of the first off-world Imperial Compliance action ever undertaken by the early Legiones Astartes.