The Holy Empire of Solaris
Solaris seems for most of the game to be an entirely military state. The bulk of the population is located in the capital of Etrenank, which floats several thousand meters above an island at the center of the map. Four gates conceal it from prying eyes and protect it from invasion. The only hint we get of their presence is through Gebler, and in Episode IV, the Soylent System, which was first based on the surface.
Leadership: Emperor Cain
Characters: Elehayym, Billy
Because of the stretch in resources, due to their location in the sky, Solaris uses the Soylent System to recycle test subjects and disobedient slaves as food for the masses, complete with drugs to keep them in check. This is unknown to all but the highest-ranking officials - and I bet they import their food. ^.^
Leadership and the Class system
"Solaris" as a country was founded by Holy Emperor Cain, and built at the beginning of the 9000 millennium. Before that, they were a ground-dwelling people like everyone else, but they probably don't mention that in present-day history classes. In theory, Cain is at the top of the food chain, with the Gazel Ministry just below him, but after the Solaris War and Sophia's death, Krelian became the true leading force in the country. He created many of the systems we see in place during the game, and he's known as the 'Prime Minister', though everyone knows he might as well be Emperor. Ramsus, who probably comes closest to these people in power, was also his handiwork.
The civilian population is divided into three categories: first, second, and third class citizens. First Class citizens are known as the Gazel, and are assumed to have pure Solarian blood and old family lines. Elly and Jesse are supposed to fit into this category. They're typically (but not always) defined by very light coloring - pale hair, blue eyes, and porcelain skin. This is the smallest class, probably what you'd call a dying breed. ^.^
The Second Class citizens are families that have lived in Solaris for several generations, but cannot trace their roots back to the founding of the country. Chances are, they don't have a trace of pure blood unless a Gazel married into the family - probably very unlikely. These people are usually descended from the slaves in the Work blocks in Lower Etrenank. The practice of "upgrading" citizens started when the Gazel population began to decline, and it was clear they simply didn't have enough bodies to keep the city running smoothly. It's possible this group, more than the others, is subject to genetic manipulation meant to optimize their usefulness to the government and create as pure a race as possible. Like the Gazel, they're indoctrinated with certain ideas, namely a contempt for surface-dwellers and slaves, and the need for human perfection.
Third Class citizens are considered slaves. Their number is made up of surface-dwellers kidnapped from their homes and dumped in the worker blocks to procreate and do all of the dirty work the real Solarians don't want to soil their hands with. They're considered sub-human, and one misstep can get an entire block killed, or "reprogrammed". But these people are Solaris's saving grace. Without them, there would be no one to upgrade to Second Class, and no hands to do the work necessary to keep the city running. Krelian gets many of his test subjects from this pool of people, but he probably grabs them before they're assimilated into the system.
Based on what we see in the game, Gebler and Jugend seem to dominate Solarian society. We don't really meet anyone who isn't in the army at one time or another. I know civilians exist, somewhere. ^.^
Anyone who wants to join Gebler has to first attend the Jugend academy. It's something like a private high school. First Class students enter at thirteen, and Second and Third Class students might start a year or two later, but everyone graduates by age seventeen. (The profiles of Elly, Jesse, and the Ex-Elements all confirm this range.) They undergo intensive training in tactics, fighting technique of choice, and the sciences. If other subjects are available, they weren't mentioned in the game.
Jugend's purpose is to breed the perfect soldier. Until recently, only First and (maybe) Second Class citizens were allowed to enter, and the academy was closed to the slaves until Ramsus changed the school's policy and began accepting recruits based on ability instead of birth. The most important requirements for entering are ether rating and IQ - extraordinary ability in either or both will automatically earn a ticket into the school.
Upon graduating, students are filtered into Gebler. Depending on what one specializes in (I assume they have something like a major system, where you can choose a particular focus), soldiers can join the air or ground forces, intelligence, or some kind of clerical job. And depending on openings, it's possible to be filtered into an elite group such as the Elements. But earning a position like that takes above-average talent - specifically in ether. I don't know what the standards are for the Guardian Angels, but they are probably the highest eschelon of soldier Solaris has to offer, above even the command staff. Present-day Guardian Angels include Hyuga Ricdeau, Kahran Ramsus, and Miang Hawwa.