The Selenar gene-cults were the ancient masters of genetic craft who dwelt upon Luna, Terra's moon, hoarding secrets of human augmentation that predated the Age of Strife. Cloistered within moon-spanning temple-laboratories, these matriarchal savants worshipped the science of the gene as a sacred mystery.
When the Emperor sought to perfect his greatest work, he turned to the Selenar, whose artistry was woven into the creation of the Space Marine gene-seed. Their knowledge shaped the transhuman warriors of the Legiones Astartes, and their alchemy underpinned the enduring might of the Emperor's crusading legions.
Yet reverence turned to subjugation. When the cults balked at surrendering their deepest secrets, the Emperor's forces broke their independence and stripped their sanctums bare. The Selenar endured only as vassals, their once-divine mysteries reduced to instruments of a greater and colder design, their moon a mere adjunct to Terra's ambitions.