"How the hell are we supposed to fight against that?!"
"We pray to whatever God is out there that we never have to battle them. THAT is how."
The Khazard'Vaari (singular: Khazard'Vaar) are an ancient species of transcendent cybernetic beings, having roamed the universe for an unknown period of time before humans and other sentient species did so. They are the creators of the archaelects, the Empyreals and the first wielders of psionics, with the few survivors being some of the most powerful psykers in existence.
The word 'Khazard'Vaar' in their language translates to 'he who embraces the machine', referring to their immortalisation as a result of advanced mind-transfer techniques.
The origins and early history of the Khazard'Vaari are unknown, though they are much older than almost every other sentient species in the galaxy, with the possible exception of the race responsible for the creation of Comet Ituyle. It is known, however, that they are a species that seeks infinite knowledge and perfection. This scientific quest led them to construct mechanised, immortal bodies for themselves and to develop technological necromancy, their progress reaching its apex with the creation of the 'phylactery ships' that granted the elite of Khazard'Vaari society almost godlike psionic power.
At some point before the evolution of humanity, the most powerful of the Khazard'Vaari, the Machine King Vaar'madr, disappeared, plunging the species' once-great empire into total disarray as factions began to compete with each other for leadership. For millennia, the inactive phylactery ship occupied by Vaar'madr would drift lifelessly through space unbeknownst to his warring subjects before he crash-landed on Earth in 1907.
Relevance to the narrative
Though Vaar'madr was all but destroyed after he attempted to enslave humanity and his omnipotent technology scavenged for their own use, many attempts were made by lone Khazard'Vaari to hunt for the missing Vaar'madr, with several coming extremely close to locating it. The cyberlich Qh'naaz even pinpointed the exact location where Vaar'madr crash-landed and where his successor, an 'Optimised Transcendence Acceleration Nexus', was built, but her departure from Earth was cut short when she was struck and disabled by a Soviet nuclear warhead in 2013, crash-landing close to Chelyabinsk.
Though she lost the necessary coordinates when her phylactery ship was broken apart in the crash, Qh'naaz successfully eluded the human soldiers sent to capture her and managed to escape to North America. She hid in the Rocky Mountains for 65 more years before she was discovered in 2078 by Jedidiah Rogers, who was seeking passage across the Pacific Ocean to lead his people to safety. The lich agreed to assist him and even granted him powerful psionic abilities of his own, handing him the Starkiller tablet that she had constructed on the condition that he help her locate and retrieve her ship's missing navigation computer. In spite of initially intending to use Rogers as a pawn to further her own ends, Qh'naaz eventually and genuinely became friends with the ork, even after they learned in 2134 that the computer had been salvaged and destroyed by OTAN's forces. They also, however, discovered that the archaelect had used its old body to father a human child, Elena Trotskaya.
In 2135, another cyberlich, Yah'thuzol, arrived in the Sol system, briefly skirmishing with OTAN on the system's outskirts before being forced to retreat after facing imminent destruction. He did, however, succeed in making contact with Qh'naaz, his sister, who in turn introduced him to Rogers. It was Yah'thuzol who suggested the kidnap of Trotskaya in order to locate the OTAN Complex, beat the archaelect in a surprise attack, and claim the immense power and knowledge of Vaar'madr for himself, Qh'naaz and Rogers. While Yah'thuzol was unable to approach Earth himself, otherwise he would attract the unwanted attention of OTAN as well as the other archaelect present and be destroyed, Rogers and his lieutenant Lavr Krapotkin were able to infiltrate the Baikonur spaceport and hijack a Burlak-class interplanetary freighter to provide a distraction to get Qh'naaz off of Earth. After the lich was reunited with her brother, the two continued to make use of Rogers' invaluable assistance until he was slain by Trotskaya in 2152, much to both of their surprise and great frustration.
After Rogers' death, Qh'naaz and Yah'thuzol gave up seeking the power of Vaar'madr and left the vicinity of the solar system empty-handed. Twenty-three years later, they were found by the blue vizier, C'shaanj, who was searching for Vaar'madr with his band of loyalists. The liches were crucial in navigating the Khazard'Vaari loyalists to Earth and reuniting with their machine monarch, joining their former nemesis Trotskaya and helping to create the alliance that would eventually form the Mechanocracy of Mankind.
Knowing that the vizier would lend his assistance should it be requested, OTAN concealed a secret message in the Golden Record sent aboard the Voyager spacecraft for him to find. However, Voyager was intercepted by a Utannic fleet commanded by Yuga Valeris. Learning of the presence of the two archaelects guarding Earth, Valeris launched an all-out invasion of Sol in order to claim their power herself and use it in the Infinity War. Though Valeris never came even close to defeating the human race, having been outfought and outsmarted by Frenkish Empress McKenzy Tandi on every level, General Vaasi Idris, House Valeris' finest ground commander, nearly seized the OTAN Complex and subjugated the archaelect housed within for himself. However, he was defeated and killed by Trotskaya and Golovkin after a ferocious battle.
Through Rogers, Yah'thuzol and Qh'naaz also learned of Alain's quest of personal revenge against Victor Golovkin, Trotskaya's second-in-command and lover, and knew of the Flight of the Polunochnaya. Aware that they were unable to chase her into the Imperium of Sidhae personally, lacking interdimensional travel technology and the capability to obtain it without alerting the archaelects, Qh'naaz recruited the assistance of Tz'shir'nagul, a prominent member of the Empyreal Devastator caste, to infiltrate the Mechanocracy, pass through a portal to Imperial space and kidnap Trotskaya. (wip)
The Khazard'Vaari are actually a largely peaceful race, preferring to be left alone in isolation to embark upon their scientific pursuits rather than waging war with a xeno species that it considers so lesser than themselves that they are not even worth fighting. They are not, however, above manipulating them for their own ends, sometimes guiding entire civilisations along the lines that they set in order to obtain the knowledge that they seek. When said civilisation has expended its usefulness to them, they typically either obliterate or assimilate it, depending on how much of a threat that said civilisation is perceived to be.
Only after the establishment of the Mechanocracy of Mankind does the Khazard'Vaari civilisation adopt a truly-warlike nature as some of the most faithful servants of Supreme Leader Elena Trotskaya. For instance, they played an instrumental role in the Schism War. Their role was most notable when the cyberlich Thaan'kor opened a portal directly from Vyyrahk to Earth, thus allowing Trotskaya to assault the very heart of the Pan-Terran Imperium with a gigantic invasion fleet.
The ultimate motivation behind the Khazard'Vaar species' constant knowledge and power-seeking is their own pursuit of the perfect being, to elevate themselves as a race of infinitely-powerful machine gods.
- The Khazard'Vaari are heavily inspired by the Reapers from the Mass Effect franchise, as well as incorporating elements of the Necrons from Warhammer 40,000.