In approximately 10,000 BCE a Termelern attempt to uplift the human natives of this worlds was abandoned in place.
The Humans took over Atlantis and the remains of the technology that the Terhmelern left, and culturally evolved from there.
On Atlantis Prime, there is Atlantis and subsidiary colonies. Atlantis is ruled by Solon, the Law-Giver. Solon is a relatively passive King, until a rebellion threatens his over all authority. Then he hits the offenders like a ton of bricks.
Atlantean Language and Culture remain relatively Static. So has the Advance of Technology. Solon's notions of governnance are clearly Platonic in nature, leading generally to stagnation except in lawless, anarchic areas.
The Armed forces of Atlantis are good at what they do (Mainly counter inurgency) and relatively well armed.
Visitors to Atlatnis find it a one-way trip unless they are very lucky. All the known Rings are guarded from the Planet Side. Solon has, at different times, trained cadres of Fringe Worthy Humans, but so far has been unsuccessful at locating the knowledge or tools he seeks.
Technologically, Altantis Prime is about the same Technology Level as Hatsumi Earth in 1976 or so. The Technology of this world is robust and evenly distributed. However it is not plentiful. Oil and coal are restricted use items. Nuclear and hydro-electric energy generation are the largest concentrated sources. Many farmers process animal wastes for methane to burn for electricity generation.
Telephones, radio and television are seen, but are expensive items. Small towns often have community telephone centers and television watching theaters.
Trains are used, but are expensive. Motorvehicles resemble Earthly off-road vehicles, because they need to travel dirt roads.
Dirigibles are the prefered form of air travel. The Military has turbo-props and even Jets but they are rare and mostly limited to executivee transport uses. Military Dirigibles hover over contested areas and rain bombs and gun fire from above. Atlantean troops carry submachine guns and assault rifles.
Larger Caliber rifles and handguns remain popular among the freemen and castes allowed to carry arms.
All mechanical designs are old and well developed. An Atlantean internal Combustion Engine will not be as complex as a 2013 Hatsumi Earth Model, but will be robust and last nearly forever - And be priced accordingly.
So the landscape sort of resembles a weird 1930s, but different.
The Culture of Atlantis-Prime is stratified. It is caste-ridden. In theory there is some mobility between castes, based on intelligence and education. In this way it resembles the Confucian system of China. However, in practice, the system is slated towards stability and consistency, not rewarding intelligence.
Entertainments are often pretty caste specific, and follow truly ancient formulae.
Most people are Proles. Working poor. They have a few rights, But must ask permission of their local Council to do much, and such permission is frequetly denied by default.
Slaves are actually fairly rare. Slaves are people convicted of heinous crimes, or Rebels against the accepted order. They live in ccarefully controlled conditions - they usually aren't free to roam about. Exceptions are sex workers - slaves who for reasons of personal attractiveness are assigned to the sex trade. The sex industry is not illegal but it is poorly respected.
There are Freemen, who came become entrepreneurs and technical experts. A Prole edducated in a technical field in the military may become a Freeman upon the end of his service.
Freemen may hold public office and vote in general elections.
Land Owners' are a step above Freemen on the food chain. They form local councils (Think of City and County Councils annd Boards) and control local budgets and law enforcement forces.
'Nobility - These people have been awarded titles. These titles go with land Fiefs which are owned by Solon, but managed by Nobles. These range from Knights, who roughly equal Land-Owners in status, to Dukes and Arch-Dukes who in Solon's Inner Circle.
Such Nobles are chosen by Solon based on recommendation, performance or just Solon's whim. The Highest of Nobles form an executive council which advises Solon and proposes Mininters for his empire. The Ministers and Bureacrats manage the details of the Empire.
If Solon becomes displeased with a noble, minister or bureacrat, they usually don't survive the experience. If they're lucky. Stories of broken men and women sold to the most hellish frontier brothels, who turn out to be former favorites of Solon abound. Such justice is swift and implacable. Rule one of Atlantis is that Solon is boss. If there's any question, Solon will probably execute you in public to make an example of rule numbeer one.
If Solon Especially likes someone, or in impressed with their intellect, he may may them King of a region. A King is just a more independant Arch-Duke. But the title does descend by default to the King's named heir. A King May experiment with economic and social arrangements within his territory.
Examples of Solon becoming disspleased with such a subsidary King include the first uses of atomic weaponry on Atlantis prime, and other blood soaked examples.