The Selenar, also called the Selenite gene-cults, were a group of religious cultists settled on Luna, the moon of Terra, who possessed some of the most advanced genetic engineering technology in the human-settled galaxy during the Great Crusade and Horus Heresy eras.
The Selenar were an ancient order, having existed in one form or another on Terra and then Luna since long before the birth of the Imperium of Man.
Whatever their title, the cult had always possessed a single goal -- to keep the power of true creation out of the corrupt hands of Mankind. At some point during the Age of Strife, they became the rulers of Luna.
The Selenar were divided up among several different cults with varying versions of their ideology which sought to use potent genetic engineering techniques they had developed to resurrect their cultists through multiple lives created through cloning.
They hoped in this way to ultimately create the perfect expression of each of several different human archetypes they had identified.
The Selenar were conquered by the early Space Marine Legions during the First Pacification of Luna in ca. 798.M30, and would go on to use their technology to help the Imperium of Man accelerate the development of new Astartes for the Legions during the Great Crusade.
However, the Selenar never came to terms with being conquered by the Imperium, and mounted several notable instances of rebellion against Imperial rule before their last remnants were destroyed following the end of the Horus Heresy.
Origin of the Magna Mater
During the First Pacification of Luna by the newborn Imperium at the start of the Great Crusade, the ruling Selenar High Matriarch Heliosa-54 charged the Selenar gene-witch Ta'lab Vita-37 with safeguarding the Magna Mater from the forces of the Emperor of Mankind.
However it seems that the device was eventually acquired by the Emperor after the conquest of Luna and the Selenar, as the Magna Mater eventually was used to store copies of the genomes of each of the twenty Primarchs.
This genetic material in turn became the source used to create the gene-seed for each of the original twenty Space Marine Legions and later the improvements to the gene-seed made by Archmagos Dominus Belisarius Cawl to create the Primaris Space Marines.
First Pacification of Luna
This early Imperial campaign in ca. 798.M31 was the first operation mounted by elements of the early Space Marine Legions beyond the skies of Terra. The Unification Wars were still raging across the surface of Mankind's birth world at this time.
Luna was the bastion of a conglomeration of resurrectionist gene-cults whose members believed that human nature was both fractal, fractured and transcendent.
Each of these Selenar gene-cults clung to a different set of archetypes. Every cult member was a product of creation by the Selenar gene-wrights according to formulae crafted in the Dark Age of Technology. Resurrected in body time and time again they sought to distill the true personification of a single human archetype.
In their subterranean complexes the cults were powerful, insular and resistant to the Imperial Truth. The Imperials would have normally dealt with these insular cults in the usual matter they handled all of the other Terran factions and techno-barbarian states that refused to accept the rule of the Emperor of Mankind -- by obliteration.
The fact that the Selenar gene-cults had something that the growing Imperium needed complicated that position. The Selenar returned the Imperial entreaties for alliance with silence. As the threats of the Imperium soon began to outnumber its offers, the Selenar cults began to gird themselves for war.
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. To this task the Emperor set the three of His newborn Space Marine Legions most suited to this purpose on what some Imperial chroniclers name as the first true battle of the Great Crusade.
The as yet unnamed XVIth Legion had been chosen to serve as the Space Marine force's vanguard, and had brought its full strength to bear. Cutting power to their assault craft, the Astartes of the XVIth Legion drifted silently towards Luna through the void like arrows fired into the night.
As the smaller wave of assault craft belonging to the VIIth and XIIIth Legions approached the airless world, the Selenar defensive weapon systems embedded in Luna's surface lashed the oncoming Imperial force. The XVIth Legion's assault craft, unlooked for and unseen, struck their targets like a dagger in the night.
Within six solar hours of the first shot being fired, Luna had been pacified and brought into Imperial Compliance, the first off-world conquest of the Imperium of Man. Faced with annihilation, the surviving Selenar cultists bent the knee instead, the surrender communique of High Matriarch Heliosa-54 transmitted to Terra calling for the Emperor to "call off his wolves."
Broken and humbled, the enslaved gene-wrights of Luna would help forge the next generation of Space Marine who would carry out Mankind's conquest of the stars. As for the XVIth Legion, they had earned their name -- the Luna Wolves.
Always resentful of their conquest by the Imperium and the use of their technology for the Emperor's purposes, the Selenar engaged in an act of shocking sabotage during the Great Crusade. They engineered a virus that infected and destroyed much of the gene-seed stocks of the IIIrd Legion.
However, the IIIrd Legion's numbers were so reduced by the disease that the renamed Emperor's Children were forced to fight for many solar decades alongside the Primarch Horus and his Luna Wolves until their numbers could be replenished with new gene-seed derived from the Primarch's genome.
Heavily involved in attempts to accelerate the development of new Astartes for the Space Marine Legions during the Great Crusade, the surviving Selenar had sought ways to improve upon the Emperor's genetic designs for the Space Marines.
Unfortunately, all their efforts failed, and the supposed "Ur-legionaries" turned out to be mutants who were often mindless brutes as a result of the constant pain they endured. Some developed multiple eyes, limbs and even heads.
Even more disturbing, several of the Ur-legionaries developed facial features that closely resembled the appearances of the Primarchs.
After the project suffered from repeated failures, the Selenar decided to abandon the Ur-legionaries and admit that they did not know how to enhance the Emperor's original design.
All but 10 of the failed Ur-legionaries were euthanised and the gene-labs where the project had been pursued secretly beneath Luna's Herodotus Omega dome were sealed.
At some unknown point after the conquest of Luna, it is known that the Selenite gene-cults were ultimately purged by the Imperium due to their rebellious behaviour.
However, at least some elements remained on Luna and still possessed their genetic engineering technology and their cult structure at the time of the Solar War.
It was these Selenar who had sought to aid in the development and enhancement of the Legiones Astartes during the Great Crusade.
Shortly before the Siege of Terra began, during the storming of Luna by the Sons of Horus forces under the command of First Captain Ezekyle Abaddon, the leader of the surviving Selenar cultists, the High Matriarch Heliosa-78, refused to carry out her orders from Rogal Dorn, the Praetorian of Terra, to destroy the genetic engineering technology that created new Space Marine gene-seed in order to prevent it from falling into the hands of the Traitor Legions.
Hunt for the Magna Mater
A group of Loyalist Space Marines from the Loyalist vessel commanded by Captain Cadmus Tyro infiltrated the lunar Herodotus Omega dome to aid the gene-witch.
The Traitors pursued and in the resulting firefight, the gene-witch was mortally wounded by the Justaerin's assault. Knowing that her death was imminent, Vita-37 reluctantly entrusted the Magna Mater to the Astartes of the Sisypheum.
To aid their escape, she unleashed the 10 surviving Ur-legionaries upon the Justaerin, a group of mutated Astartes unsuccessfully enhanced by the Selenar centuries before in an attempt to improve existing Space Marine gene-lines.
The Ur-legionaries were able to overpower and kill most of Trastevere's squad before they followed Vita-37 into death.
However, this aid proved to be enough to allow Tyros' Astartes to escape with the precious artefact aboard the Sisypheum.
Though all of the Strike Cruiser's crew were later slain escaping from near-Luna space with the artefact save for Nykona Sharrowkyn of the Raven Guard, the Magna Mater would eventually fall into the hands of the Primarch Roboute Guilliman after the end of the Horus Heresy.
- High Matriarch Heliosa-54 - The Selenar high matriarch at the time of the First Pacification of Luna by the Imperium in ca. 798.M30. Heliosa-54 handed the Magna Mater over to Ta'lab Vita-37 and told her to go into hiding so that the Imperium could not claim the artefact. She then erased her own memories of both Vita-37's existence and what had been done with the Magna Mater.
- High Matriarch Heliosa-78 - The Selenar high matriarch at the time of the Siege of Terra in 014.M31. She refused the order of the Primarch Rogal Dorn to destroy the Selenar's gene-seed creation technology. Instead, to maintain her own position of power, she swore the Selenar's loyalty to the Warmaster Horus. She promised Horus that she would deliver new Heretic Astartes to him to replenish his Legions.
- Ta'lab Vita-37 - The Selenar gene-witch charged with safeguarding the Magna Mater who eventually handed it over to the Imperium through the crew of the Sisypheum during the Siege of Terra.
- The Horus Heresy Book One - Betrayal (Forge World Series) by Alan Bligh, pp. 80–81
- Chirurgeon (Short Story) by Nick Kyme
- Fulgrim: The Palatine Phoenix (Novel) by Josh Reynolds, Ch. 4
- The Solar War (Novel) by John French, Chs. 20-22
- Siege of Terra - Sons of the Selenar (Novella) by Graham McNeill, Prologue, Chs. 6-7, 10-11