Unathi history is extremely ancient, and is therefore divided into several "ages". The specific date of eras are not strictly important until events of modern times.
Archaic Bomus (25,000 BCE)
Moghes had forever been ruled by Unathi who have set themselves up as living gods that ruled collections of city-states, and society was built around them. They were called the Ensi. The Ensi were resisted by a successive series of civilizations, scholars, and inventors that worked to proliferate their knowledge and the dream of progress. This struggle played out for twenty thousand years.
Old Bomus (2000 BCE)
Eventually, one of these leagues managed to colonize Yzali, the second habitable planet in the system. In retaliation the Ensi destroyed the colonizers' cities on the homeworld and the colony was left to itself. The colonists on Yzali, despite being abandoned, proliferated and became a well-organized, complex technocratic nation that exploited the planet and each other in a relentless drive for what they defined as progress.
After surpassing its home world, Yzali dominated the Bomus system with advanced technology including android and cyborg soldiers called Akran - the precursor of modern Aut'akh. With its own biosphere tapped out by the end of the era, Yzali Techno-Princes colonized the barren world of Zakkeran and terraformed it, and then eventually turned with the power of two worlds to dominate the old home world of Moghes, disrupting the rule of the Ensi with high technology.
Shortly before the coming apocalypse, yet another Yzali colony ship, fully automated due to a lack of FTL, was dispatched to a barren world called Myishum orbiting a neighboring white dwarf in a trip that would take two thousand years - just in time to reach its destination when The Disaster struck.
The Disaster (2000 CE)
Around 2000 CE by sol reckoning, a massive solar flare wiped out the nascent solar Yzali empire, casting them into the role of techno-barbarians while Moghes, with its Ensi well equipped to rule over a technological backwater, enjoyed a resurgence of power in the otherwise post-apocalypse as Yzali rebuilt a new layer over the ruins. Only technology stored in secure caches or otherwise shielded remain spared, and in modern times are called Pre-Disaster Tech. This technology can do wondrous things akin to magic.
Middle Bomus (2300 CE)
With the Yzali religious awakening leading to Hartism, the Tech-Princes that ruled the nascent new powers of their world sought ever-increasing ways to improve themselves. Breakthroughs in mind-mapping allowed true cloning and potential immortality. But after the harrowing discovery of Clone Madness, Tech-Princes banned the practice in their realms, not wanting a "mad" clone to make them look bad. Only the most vain Ensi of Moghes took in the practice, leading to the 325 year reign of Hal-aman “the Eternal” - also known as Hal-aman “The Aberration”.
In the 2300’s arriving colonists, mostly Jesuit missionaries, encountered the system in a damaged and decrepit colony ship, long since cast adrift by an errant solar flare. Rejected by Moghes and fearing inhumane exploitation by Yzali the majority escaped to Zakkeran, joining the Unathi inhabitants there to form a new syncretic culture. Eventually the Prophet Sassur escaped Moghes and became a translator for the Jesuit mission on Zakkeran. He eventually became a religious leader and then Prophet, galvanizing the Zakkeran population against the colonizers, managing to survive until eventually passing of old age.
In this same era a group of Aut’akh stole a small fleet of Yzali trade ships, faking its loss in a pirate raid and fleeing to hunt for the lost colony ship of Myishum.
New Bomus (2400 CE - Present)
In modern times Yzali has once again become a hedonistic technocracy, where ambitions tend to be tempered by luxury while merchants and scientists obsess on lost technology from before The Disaster. Moghes continues to resist change as best it can, working to increase the Ensi’s power to better enforce its conservative order. Caught in the middle, Zakkeran struggles to find a new way, with radical and revolutionary visions sweeping through the planet as its syncretic human and Unathi culture works to throw off the two powers and go their own way, while the Aut'akh continue to seperate themselves from the entire messy affair with distance and detachment.
While the four nations had learned of alien life through the arrival of the lost Jesuit missionaries in the Middle Bomus, the arrival of formal expeditions from the other spacefaring powers led to Unathi emissaries being brought out to the wider galaxy. The shock at seeing the sheer size and breadth of the galactic community (and their warships) shook the emissaries to their core. When they returned the Yzali, Moghean, and Zakkeran emissaries spent over a decade hammering out an extremely tenuous and in-name-only alliance between the three planets called The Hegemony.
Present Day
Moghes has incredibly complex and shifting realms of city-states and realms. However half of the planet has been conquered by Hal-aman and his hive-mind of clones.
Yzali is technically a single world government, but in reality its glittering cities - which can even float across the sky or web their way under the oceans - are ruled by petty, vindictive, paranoid, and utterly self-obsessed Tech-Princes.
Zakkeran remains a world of semi-nomadic communes that share the world with colonizing Moghean and Yzali powers, and work to assert themselves and establish a new shining city on a hill.
The Aut'akh remain aloof and distant, technical members of the Hegemony but unwilling to provide much cooperation to their former slavemasters. They seek to continue taking in the unwashed masses yearning to be free - and protected by twenty thousand kilometers of deep ocean.