The prime is the main portion left of Sigil that broke away from Mechanus after it was destroyed, it generally lines up with Core-Junction on the plane of Xelanis, so that it can stay in contact for transporting planar tourists, it is all run by the ancient mechanus Primarch and Axiomite, Elmod Hashnerfell, he is in charge of maintaining order between all the races and creatures that pass through the Prime,
In the Dwell or Astral, there are 3 main companies that produce out here, Balanced Engineering, Ammon Aspirations, and Starborn Frigate. Though these are mostly owned by their Material plane centers, they are treated as fairly independent, thought especially useful materials are shared back within the company.
All three are represented on The Prime, all follow and work with the Primarch, though they have their own stations out in the Dwell, they will pay for planar ranger support, and out here they are rivals, but not enemies. It is considered standard to assist any company ships that request assistance, for a 10% of the sales from that recovered ship, unless the crew is all dead, then you get 5% and the other 5% is sent to the families.
Starborn Frigate generally pays for most of the exploration, while BE helps to create waypoints in the Dwell that ships can retrace paths, Ammon Aspirations do most of the commercial and civilian transportation. This is not to say they do not need weapons, new planes and area uncovered sometimes come with races the King has imagined as part of pirate stories, or ones that make their own ships.
Material Plane - Xelanis
XelAnuli - party moon
Scorn - Void Moon - shifting to rotate around the plane of fire
The Constant
The known
The Astral or Dwell - The 3 Horsemen are out here, the King and Queen.
The Prime - this is the main center hub plane, controlled by the Primarch, Balanced Engineering, Starborn Frigate, and Ammon Advancements are the main companies that operate.
The Elemental planes - Air, Earth, Water, Positive, Negative, and Fire - Though fire is in a process of genesis with the plane of Scorn.
Broken Laws - the many broken and worn down gears of the mechanus that are scattered separating the know and the akashic.
The Akashic
Infernal planes
Celestial
Abyssal
Chaos planes
The Imagined
These are the new planes and worlds that are coming into being as the King is read more and more stories, ships are sent out to see if the new races are hostile, or if there are new materials that can be used because of how random it can be out here, most ships bring their own oxygen and sealed ships to make sure they can remain safe against unknown things past the known realms.
The Watchers
If you run into any of the watchers, or their astral knight assistants you have gone too far and are potentially entering quarantined areas.
The Lost
Mobius Library
First World