Unlike their forebearers, the Lamenters were not created by the hands of their benevolent Emperor, but by the hands of mortal men. These mere men sought to perfect a design wrought in the ancient gene forges of humanity’s distant past, using archaic and forgotten techniques of genetic engineering by the man whose intellect and force of will pulled the entirety of humanity from an unknowable dark age, whose knowledge outweighed that of all the combined efforts of the greatest minds of the Mechanicum. Once again pride had proven to be the source of humanity’s sin.
At the twilight of the 35th millennium, these men within the Adeptus Mechanicus Magos Biologis sought to weed out and hopefully eliminate the genetic deviations that had arisen in the gene-seed of a handful of the first founding Adeptus Astartes Legions. The results of this monumental task were then to be poured into an attempt to create Space Marines that were more akin to the legendary Primarchs of ages past than the current Astartes. The millennia-old research of which was based on data fragments left behind by Archmagos Dominus Belisarius Cawl before his sudden disappearance immediately following the Horus Heresy.
Despite warnings against their hubris, Genetors of the Adeptus Mechanicus began the risky experiments. For the Blood Angels gene-seed the black rage and the red thirst deviations were their explicit focus. To further eliminate other perceived “weaknesses” the Mechanicus also attempted to hybridize several gene seeds. A heresy to the mainstay of the order, this process would theoretically create chimeric chapters with the best attributes from each gene host. Rumors churned throughout the sector that the project had access to all twenty of the gene-seed profiles, loyalists, traitors, and forgotten alike, pushing the work further into the fringes. However, all attempts to shut the program down by administrative and military channels were met with resistance at the highest level of authority.
With promising results of their haughty efforts, the Adeptus Mechanicus Genetors began crafting organs for transplant into the thousands of humans that had been selected for the audacious program. Many of these men who gave their lives willfully to become selfless defenders of humanity would become something they never imagined. With their emergence, the 21st founding was laid, the largest since the Second Founding, immediately after the erratic times of the Horus Heresy. Humanity was desperate for more champions, but the fruits of the Mechanicus’ labor were to become spoiled.
Upon completion of the initial batches, rampant mutations, susceptibility to chaos, and outright insanity plagued most of the chapters that emerged. Entire swathes of the implanted subjects could no longer be categorized as strictly human. They became something fundamentally different. Many of the subjects that began mutating were immediately executed on site to prevent the grotesque monstrosities from manifesting their full power. As each sarcophagus opened, a new horror was unleashed, birthed into the world with inhuman sound, promptly followed by the sound of gunfire.
Other subjects, that were not as badly mutated, seemed to be prepossessed with a tendency to chaos, leaving the laboratories behind to seek out their brothers in the warp. Entire chapters, drawn like moths to a flame fought their way out of the hidden Mechanicum facilities with only a handful of survivors reaching the surface, taking whatever means of conveyance available to seek out the warp and forge a path of ruin.
Despite the anarchy, there were but a handful of chapters such as the Minotaurs and the Lamenters that were deemed stable genetically with no defining physical mutations to speak of. Numerous other chapters such as the Black Dragons, Flame Falcons, and Firehawks would all develop inhuman mutations shortly after their deployments into the ranks of the Adeptus Astartes. Many of these chapters would be hunted to a man by the Inquisition. Others, such as the Firehawks would be lost to the warp, following a dark trend for all 21st Founding chapters who seemingly acted as magnets for chaotic warp activity, something even the Lamenters wouldn’t even be able to avoid. A few surviving Chapters with physical abnormalities walk a razor’s edge between service and sanction. The Inquisition is always watching, waiting to annihilate these chapters at the first sign of suspected heresy.
Because of these terrible circumstances, the founding earned the moniker “The Cursed Founding” in Inquisitorial circles. Those that once protected the program could no longer ignore the evidence that lay in blood before them. The 21st Founding was a failure. When the exterminatus orders came down, and the fleets arrived to deliver the righteous destruction upon the ill-fated project, the surface of the planet housing the facility was already destroyed. All traces of the facilities existence were already gone, perpetrated by an unknown assailant. Many feared chaos involvement. Whatever records were left in the aftermath, the databases, their backups, even the Adeptus Mechanicus Genetors that were rotated out of the program, were all purged and erased from existence. The Space Marine chapters that would be recruited to help hunt down their wayward brothers would learn of the project in whispers and half-truths. They too adopted The Cursed Founding as an identifier for their burdensome work. From there the myth of The Cursed Founding spread and with it grew the stigma the remaining few Cursed Founding chapters loyal to the Imperium would bear for the rest of their days.