/tg/Station 13

Eris takes place in the grimdark future of the 24th century in the Canis Major galaxy (colonised by the now-defunct human Alliance and cut off from the Milky Way Galaxy) onboard the Cosmic Exploration Vessel "Eris", a privately owned vessel sponsored by a multitude of factions operating as departments upon it (Moebius Laboratories functions as medbay and research, the Technomancer League as Engineering, Ironhammer as security, Asters Guild as cargo and Frosen Star, Neotheology and the Hansa Trade League as its backers). The most notable faction out of them all is Neotheology.

To cut a long story short, Nanotrasen got taken over by religious fundies and got rebranded as NeoTheology, controlled by the Church of Cyber-Christianity. Neotheologians believe that Judgement Day is coming soon but God gave Mankind technology to create a civilisation of righteous people to fight it, as its Last Chance. The most important thing to know about Neotheology is that only they possess cloning technology, and only Christians may be cloned in a highly ritualised ceremonial machine - its operation is restricted only to those in the Church hierarchy.
When a Christian is first baptised, he is implanted with a cruciform - an implant that effectively functions like a cortical stack. When you die, a clone is made of your body and the cruciform removed and implanted into it - effectively re-sleeving you into it with your personality and memories up to the moment of your death intact. Removing the cruciform is highly lethal and will instantly kill you if it is removed while you're alive, it is located in the chest and is visible in the skin, resembling a tau-cross. The cruciform is highly-hostile to any implant that is not itself and will literally rip them out of your body if it must.

The Eris is the Captain's personal property and he's best described as the SS13 equivalent of a Rogue Trader, being free to do what he wishes. The factions on the ship are here at his leisure (or were hired like Ironhammer, being PMCs) and he's here to turn a profit and needs to keep the factions in check (who have their own agendas).
The Syndicate, as we know it, no longer exists (Ironhammer are actually descended from them) but every faction is innately hostile to Excelsior, who are hyper-expansionist communists who use implants to brainwash people into joining their communes. Traitors and revolutionaries are Excelsior-backed.

The Eris itself is basically if someone took a space hulk and said "yeah this is mine now", stuck some thrusters on it and flew off without clearing out the xenofauna or restructuring it, so maintenance is a literal labyrinth full of loot, traps, workplace hazards and deadly creatures. And that's not counting the ones the Technomancers put up afterwards. Assistants are pretty much slaves in most sense of the words, being hired for very little or press-ganged from passing planets/ships and there are no aliens, that humanity knows of, and if it did - they'd be kill on sight.

Ironhammer security is a PMC-for-hire and are contracted by the Captain to operate as its security force. While technically each department is its own sovereign entity the Overseer (the RD equivalent) and the Biolab Officer (the CMO equivalent) can tell Ironhammer to fuck out of Moebius property to protect their interests, extraordinary situations can change this. Ironhammer distrust synthetics and hate mutants, every operative of theirs is required to exterminate any they find on sight. Ironhammer are mercenaries first and foremost with loyalty to their commander and each other coming first, and the highest bidder second.
It is perfectly possible and reasonable to potentially buy out security's loyalty from under the Captain.

Moebius Laboratories is the modern day Nanotrasen, though not nearly as influential and Neotheology make them look like jackshit compared to what the Church's Inquisitors roll around with. They're mostly known for their medical products while their inner-workings are more or less a mystery. They're infamous for rumours of unlawful abductions, experimentations and are one of the few corporations with the legal power to perform otherwise forbidden research in most systems.
Moebius will do anything to gain an edge over the competition and will hoard their research jealousy, though the Overseer is empowered to sell inventions at his own judgement.

The Technomancer League are a bunch of space nomads for the most part. They used to be very technologically dominant but a cataclysm rendered them destitute and forced to live on their feet and pay their way by plying their services as engineers. They typically live in clans, headed by a Technomancer Exultant (the equivalent of a CE) who is their clan patriarch/matriarch.You can think of Technomancers as somewhat less superstitious techpriests and you'd be right for the most part, they venerate technology and are one of the few factions with zero restrictions on synthetics. However, they're highly xenophobic and distrustful of outsiders and are given some leeway to defend engineering in whatever way they see fit, which usually means traps and mazes everywhere.
The Technomancers will refuse to abandon the Eris as much as they can, they're born, raised, live and die on ships and entire generations can be born and die out on vessels they can be found upon.

The Asters Guild is a unity of spaceports, trade stations, shipyards and factories coming together to create a monopoly on space travel. Only the Guild’s members have access to the most advanced engines, navigation devices, AIs, and cybernetics for direct connection to a vessel (it is a cyberpunk dystopia though the cyber part is still WIP mechanics wise). The Captain and the First Officer are technically a part of the Guild as Free Agents, though the Guild Merchant (the QM equvialent) is not subordinate to the Captain and operates independently.
The Asters Guild are interested only in profit margins and maintaining their dominance on interplanetary travel, any threats to that must be eliminated.