Every open-world game needs a hub, and Orbtopia is Sea of Remnants' answer — but unlike most hubs, it is explicitly evolving. The official description is that you shape the city through your choices, and it is worth taking that seriously because it is the game's answer to a very open design problem.
The sea is enormous, and the systems layered on it — fleets, companions, factions, multiple endings, meaningful choices — are many. Without a fixed point, that becomes noise. Orbtopia provides the point where all of it accumulates: it is where you return, where your fleet is based, where companions gather, and where the visible state of the city reflects the decisions you have made across the whole game.
That is the design reason the choice system is set in a city rather than spread across the ocean. Choices made at sea resolve in Orbtopia, and Orbtopia's condition is the running record of them. The city is the save file.
Orbtopia is also where the six fleet factions intersect, and that is where the character of the city comes from. Ranbo is described as Orbtopia's own — its wildest rock stars — which means the city has a scene, an entertainment culture, and an audience. Drift Bottle departs from it. The Black Baron brings the taste of the wealthy. A city with all six fleets present is a city with factions in it, and that is what makes the choices consequential rather than cosmetic.
The game's tags include meaningful choices and multiple endings, and both of them live here. The official framing ties the city's evolving state to your decisions, which means the endings are not a separate branch at the end — they are the accumulated shape of a city you have been changing for the whole playthrough.
This is why the fleet factions matter beyond combat. Who you sail with, which fleets you ally with or antagonise, and what you do in Orbtopia are the same system seen from two sides. The factions are the mechanism by which a relationship with a crew of three hundred becomes a political position in a city.
Honest limits: the public material does not document the specific mechanics by which choices alter the city, the systems behind the multiple endings, or the number and nature of those endings. What is confirmed is that the city evolves, that choices are meaningful, and that endings are multiple. If you want this page to become a real guide, the place to send it is a write-up of what changed in Orbtopia across two playthroughs — that is precisely the information no amount of trailers will give you.