Crossposting from my DeviantArt account.
This is my personal interpretation of the Mass Relay network in Mass Effect. The galactic map provided in the game serves primarily as a gameplay tool rather than an accurate representation of the vastness of space and scale of the galaxy. It is kind of hard to believe that only a few dozen settled star systems exist within the expansive universe of Mass Effect. Thus, I crafted my own vision of the Mass Relay network, showing a sprawling network that spans across numerous sectors and encompasses a multitude of galactic regions. I tried to capture what such a colossal galactic network could plausibly look like.
In the context of the Galactic Mass Relay Network, the administrative definition of a Cluster diverges from its astronomical counterpart. While in astronomy, clusters denote groups of stars bound by self-gravitation; within the Mass Effect universe, a Cluster signifies a 3D region centered around a Star System that possesses at least one Mass Relay. These Clusters are not individually depicted on the map; rather, each hexagon represents an entire sector, comprising 21 Clusters each, meaning there are a total of 86,436 clusters across the galaxy, each with at least a dozen garden worlds. Sectors, on the other hand, serve as each of the hexagons visible on the map, they constitute regions of space composed of numerous Clusters linked to the same Hub System, with 4,116 sectors in total. Supersectors emerge as collections of seven Sectors, with one Sector serving as the core linked to six other Sectors. There are a total of 588 Supersectors in the galaxy. And then, Regions, generally encompass seven Supersectors, with each Region possessing a core Supersector connected to the 2nd Lvl Primary Relay System, with a unique link to the 1st Lvl Primary Relay System. Regions may have fewer supersectors at the galaxy's edge. Finally, the Trine divisions of the galaxy resemble slicing it like a pizza into three equal segments, each boasting a Trine hub with six 1st Lvl Primary Relay Connections, serving as convergence points for circumgalactic highways. The galaxy's three Trine hubs include the Widow System, the Omega System, and the Antares System. Acting as the primary hub, the Citadel not only serves as a Trine Hub but also features Grand Connections, the longest relay connections in the galaxy.
There are seven types of Star Systems in the Mass Relay Network:
Star System - Just an ordinary star system. There are billions throughout the galaxy.
Relay System - A star system with at least one Mass Relay. The most common type of a Relay System is a star system with one Secondary Relay, an example of which is the Sol System. There are 86,436 Relay Systems in the galaxy. They serve as the central star system of Clusters.
Hub System (or Sector Hub) - A Relay System, but this time with at least one Primary Relay. Other than being the central star system of their Clusters, they also serve as the central star system of their Sectors. 4,116 of the 86,436 Relay Systems in the galaxy are Hub Systems.
Supersector Hub - A Hub System, but this time with at least one 2nd Level - Primary Relay. Other than being the central star system of their Clusters and Sectors, they also serve as the central star system of their Supersectors. 588 of the 4,116 Hub Systems in the galaxy are Supersector Hubs.
Regional Hub - A Supersector Hub, but this time with at one 1st Level - Primary Relay, making them connected to the Galactic Ring Roads. Other than being the central star system of their Clusters, Sectors, and Supersectors, they also serve as the central star system of their Regions. 84 of the 588 Supersector Hubs in the galaxy are Regional Hubs.
Trine Hub - A Regional Hub, but this time with six 1st Level - Primary Relays, being not just connected to the Galactic Ring Roads, but also being their nexuses. Other than being the central star system of their Clusters, Sectors, Supersectors, and Regions, they also serve as the central star system of their respective one-third slice of the galaxy, a Trine. Only three of the 84 Regional Hubs are Trine Hubs: Antares, Omega, and Widow.
Widow System (or Citadel System) - A Trine Hub, but this time sporting the Grand Relays, not only serving as a nexus of the Galactic Ring Roads, but also having direct Grand Relay connections to various parts of the galaxy, making the Citadel System a shortcut to anywhere in the galaxy. Of the 86,436 Relay Systems of the galaxy, the Citadel System is the hub of them all, sporting a total of twenty-five Mass Relays.