Iron Pact

The Mankind's sole remaining totalitarian regime, currently occupying the entirety of the Jupiter Subsystem. A highly militarized society dedicated to the concept of improving Mankind through a combination of restrictive eugenics (reaching all the way into the level of the jovian society being effectively divided into genetic castes) and cybernetic enhancements. A power that, while its numbers seem small when compared to the giants of the Inner System, somehow manages to play in the Solar System's first league.
It is equally hated and loved within the Inner System. While it's undoubtedly a massive problem which appears to be conducting crimes against Mankind on an almost daily basis, it's also a military powerhouse that does a lot to shield the Inner System from numerous threats dwelling in the Outer System. As a result, there are no on-going plans of the Inner System polities to overthrow the Iron Pact's government, due to the chaos that this would cause being potentially lethal to a large part of Mankind.
This, naturally, only lasts for as long as the Iron Pact doesn't attempt to openly expand. Although the key word is 'openly' - Pact is yet to conquer something outside of the Jupiter Subsystem, but pulling something into its sphere of influence is an entirely different thing.

Structure

Iron Pact is a unitary totalitarian regime, governed centrally from Callisto. Each world does has its own government, but their leadership is best treated as governors, totally subservient in front of the central government and surrounded by soldiers of the Jovian army that they have no control over. And if there is one thing that Pact doesn't tolerate more than anything else, it's governors who act too freely.
Iron Pact is led by president, who is further assisted by the Council of Five. This is all a relatively new development - until the Blackout, the Jupiter Subsystem was a facade democracy, ruled from shadows by a cabal of unelected officials (dating back to the times of the first Iron Pact). It has recently stepped up into the light, dismantling the democratic trappings of the system.
Each of the Five has a lot of power. One oversees the Navy. One oversees the Army. One is tasked with overseeing the local secret police and is, in general, responsible for rooting out dissidents and maintaining the grip on Jovian society. One is responsible for the Jovian research - which includes development of new weaponry, new improvements to human species and finding a ways to crack whatever horror crawls out of the Dark Space. The final one is responsible for foreign affairs - including the foreign intelligence of the Iron Pact.
The Council of Five is still rather unstable (with some of its members clearly struggling from backseat to frontseat governance). What's more, president Adeline Hauser-Delacroix is the Iron Pact's first president - as a result, her death will probably trigger a major succession crisis, as the succession mechanism weren't tested. Technically, the Council of Five should choose one of her descendants to become the new president, but whether this will truly occur remains to be seen.

History

The first Iron Pact was created on Earth, during the Days of Fire. Following the eruption of Yellowstone supervolcano followed by similar eruption of Phlegreian Fields supervolcano in Italy, Europe was pushed into years long volcanic winter. Naturally, this paved the way for the extremists to raise, leading to the five-year-long European War. Initially fought between various secessionists groups and remaining national governments, it was soon changed into a war between the governments and the local radicals - and then, a war between the radicals.
In the end, France and Germany were overtaken by a relatively similar branch of radicalism (under Eugene Delacroix and Karl Hauser), both systems incorporation certain elements of fascism, nazism and communism, with the former two being notably dominant. Both regimes immediately began mass-purges of political opponents (or simply people of wrong ancestry). Once that happened, they could forget about establishing meaningful and positive relationships with foreign powers, leading to them being pariahs on the global stage.
Naturally, they grew into allies. One more historical shift of alliances, akin to the France turning from Great Britain's centuries-old enemies into allies when Germany emerged as a threat. This was the foundation of the Iron Pact. Even then, it was still an alliances of pariahs - heavily militarized and with a lot of resources (and nuclear weapons), but still, pariahs. They remained isolated, landlocked between Central-Eastern Europe (dominated by the Visehrad Alliance, then part of the Alliance for the Preservation of Democracy), and the remaining countries of Western Europe (namely, Great Britain, Spain and Scandinavian countries, now parts of the Union of Progress and Freedom).
Iron Pact's existence changed from fringe pariahs into notable players following the Third World War. it was merely an addendum to the global (and beyond that too, as Luna was involved) war between the Union and Alliance. The latter struck a deal with the devil, and Iron Pact's presence protected Visehrad's flank during its battle with the UPF forces marching westward from Russia.
Alliance never intended to let Iron Pact continue its existence. But when the war ended, it was way too tired to intervene while the Iron Pact devoured the British Isles, the Scandinavia and the Iberian Peninsula. Establishing several new member-countries and beginning another series of purges, although this time it was done in a slightly less violent way. So rather than mass extermination it was neutering of those seen 'genetically inferior', with only the active enemies of state being executed.
Iron Pact has continued to exist, and even expanded by establishing (and that was a real longshot back then) its colonies within Jovian Subsystem. It also continued to degrade, losing its ideological drive and slowly getting overtaken by corruption, in a way not dissimilar to the last decade of the history of the USSR. This came to a halt when the Fourth World War started, and the Iron Pact was found wanting.
Its domain on Earth has survived the war, only to collapse soon after (in 2146). The result of its reunification was the birth of the European Sympolity, which continues on to this day. The Jovian colonies didn't survive for much longer, having politically collapsed by 2155. They were eventually reforged into the Jovian Coalition (later on renamed into Jovian Republic), country that many considered to have been merely a rebranded Iron Pact with a facade of democracy to keep the foreigners for looking for revenge for its past crimes.
This policy lasted until the Blackout. With the Solar Commonwealth collapsing, the shadow cabal behind the Iron Pact's government decided to step into the light, overthrowing (bloodlessly, as there was no resistance to this) the Jovian government. Iron Pact rose once again, ready to fight to spread its doctrine throughout the Solar System, without the falsehoods of its facade democracy to restrain it.

Demography and Population

The population of the Iron Pact is estimated at about one hundred million. It's almost uniformly human - aliens (such as sidhe and voca) aren't allowed in their entirety, and transhumans are considered a kill-on-sight target throughout the Iron Pact territory. Variants, in the meantime, aren't legally 'people' within the Pact territory, and are an open object of trade (fact normally justified as them being a failed experiment, a sideline in human evolutionary line that has, however, not 'earned' extermination with their actions as transhumans did).
The humans themselves are further divided internally between several genetic castes, depending on their genetic 'purity' and perceived 'superiority' (or lack of thereof). Those castes are varied from generally average Regulars (the 'subhuman' treatment is limited to Variants, for as long as you are a human, you are at least a Regular) through Superiors, Elites and, finally, extremely rare Ultimates.
Contrary to what one can expect, those genetic castes aren't entirely meaningless confabulations established in order to maintain a societal division. The Iron Pact's leadership continued to run genetic experiments during its period of shadow governance over the supposedly democratic Jovian Republic. While Regulars are mostly unaltered, every higher caste is technically a human subspecies (though still within the generally understood human baselines), with every subsequent level typically possessing a higher average IQ, improved strength, stronger immune system, more frequent Awakenings etc.
Especially Ultimates (only few thousands of them exist, all of them occupying the highest ranks of the Pact's governments) can be considered a massive threat on the battlefield, especially as the militarized culture of the country pushes them towards receiving combat training and combat-oriented cybernetic augmentations. The end-result tends to be a rather horrible opponent to have on the battlefield.
The genetic castes are no longer tied to skin colour (although the non-Whites are remarkably rare among the Ultimates). The logic behind it is that the legal, wide-scale genetic tampering during the Solar Commonwealth era (namely, the Humanity 2.0 Project) has de fact equalized races, making the colour of skin mostly an issue of aesthetics. As a result, every human, regardless of skin colour, is at least a Regular.

Territories

Jupiter Subsystem

Callisto - Terran Planet/Civilized World. Iron Pact's capital world. Population: 23mln.
Ganymede - Terran Planet/Industrial World. Light industry mostly. Population: 19 mln.
Io - Volcanic Planet/Industrial World. Heavy and chemical industry. Population: 14 mln.
Europa - Ocean Planet/Agri World. Iron Pact's main source of food. Population: 12 mln.
Jupiter - Gas Giant/Mining World. Many gas extraction platforms. Population: 9 mln.
Himalia - Transshipment station, shipyard complex and fleet anchorage. Population: 1 mln.

[Multiple more, minor settlements on various Jupiterian moons]

Military

Jovian Navy

Jovian Navy is disproportianately large for the local population, at least partially a result of Jupiter Subsystem being a country composed of numerous separate worlds - unlike, for example, Mars, here the concept of space travel is something absolutely basic and mundane. The result is a lot of people who have (to a various degree) 'adapted' to space, and a lot of knowledgeable engineers and spacers to recruit to the Navy.
It also relatively well-organized and well-trained, generally considered to be one of the most dangerous fighting forces within the Solar System (although it's still notably behind the major powers of the Inner System).
The current estimates of the Jovian Navy are as follows:
Capital Ships:
Four Battleships - JNS Eugene Delacroix, JNS Karl Hauser, JNS Chloe Beringer and JNS Basil Nelson.
Two Voidcraft Carriers - JNS Vasco Caldera and JNS Jonas Rehn.

All of the Jovian Navy capital ships are named after famous leaders of the Iron Pact from its early, Terran years. The list includes the two founders of the original terran Iron Pact (Eugene Delacroix and Karl Hauser). The list includes the president of France and de-facto leader of the Iron Pact during the Third World War (Chloe Beringer), the leader of the occupational government of Britain (and then, the Britain as a part of the Iron Pact) Basil Nelson, and his equivalents from Spain (Vasco Caldera) and Sweden (Jonas Rehn).
It should be noted, that two out of six people immortalized that way are considered to be genocidal maniacs by the general Mankind (Delacroix and Hauser), while the rest aren't far beneath their level when it comes to morals.
Escort Ships
Four to five Heavy Cruisers.
Six to Eight Light Cruisers.
Three to Four Escort Carriers.
25+ Destroyers
30+ Frigates

Jovian escort ships are typically named after positive qualities of character (cruisers, think 'Fearless' or 'Loyal'), moons of Jupiter (escort carriers), various war heroes of Iron Pact (destroyers) and, finally, weapons and objects (frigates, examples includes Sword, Axe, Compass etc.).

Jovian Army

The Jovian Army is a force to be reckoned with. Estimated at around four million regular soldiers, two to three hundred thousands of the elite soldiers of the VRF (Volks Reinheit Front, compared by many to the Waffen SS of the Third German Reich), and the conscription pool equalling the size of their adult population - basic combat training is something taught in normal schools, although to a greater degree for members of higher castes.
Jovian Army is disciplined, and tempered in regular engagements against pirates and Dark Space incursions. It is generally considered to be among the Solar System' top when it comes to quality, although it heavily lacks the manpower to engage in prolonged planetary warfare against more populated worlds. In other words, while the Iron Pact could potentially dismantle the Saturnyne Confederatation, every attempt to invade for example Mars can be freely considered to be a suicide.
VRF is typically composed of at least Superiors, with many Elites and some Ultimates as higher ranked officers. They are extremely dangerous, combining intelligence, drive, technical skills, numerous combat or utility augmentations and extensive ideological indoctrination.

Religion

Iron Pact generally considers all forms of religion to be an 'opium for the masses', namely those who are genetically and thus morally/intelectually inferior to the inhabitants of the Iron Pact. Harboring religious beliefs isn't something enough to warrant a purge (unless you start organizing yourself with those who think like you), but you can expected to be ridiculed and excluded from promotions (in any governmental organization) unless you abandon those.

Iron Pact

Summary
Capital: Callisto
Language: French or German
Population: ~100 million
Other Names: Jovian Republic

Politics
Government: Totalitarian Regime
Religion: State Atheism
Biostatus: Progressivists (Excl)
Cyberstatus: Progressivists (Excl)
Ruler: Adeline Hauser-Delacroix

Economy
System: State Capitalism
Megacorps: Restricted
Slavery: Supported

Demography
Baselines - Stratified.
Variants - Enslaved or Exiled.
Transhumans - Exterminated.
VIs - Exterminated.
Aliens - Exterminated.