The Rim includes all the outer planets (and their moons) beyond The Asteroid Belt.
The Rim has had a rocky relationship with the rest of Society since its founding, thus reflected in the two Moon Lord Rebellions pushing for Rim independence. These rebellions were spurred on by a lack of Rim representation on Luna and trade sanctions remaining from the First Moon Lord Rebellion, among other things.
The Rim includes all of the outer planets and moons beyond the asteroid belt between Mars and Jupiter. This includes Jupiter, Saturn, Uranus, and Neptune, and all of their respective moons. Only the moons are inhabited, as the planets are either ice or gas giants and cannot be terraformed.
Only four of the Rim's sixty-seven inhabited moons have populations greater than 100 million.
It takes even the fastest of ships months to travel to the Rim from the Core.
The Rim also includes dwarf planets, some of which have settlements that are considered colonies of the Core. Mediocre students who graduate from the Mars Institute, and presumably other institutes, as "Shamed" are often offered assignments stationed in the distant, hard dwarf planets to oversee the first years of terraforming.
Darrow's in-depth conversations with Lorn au Arcos and Romulus au Raa about societal beliefs and practices suggest that the majority of the Rim's Gold families have similar sentiments towards the Core.
Rim dwellers have a proud doctrine of honor and pride and are generally very disciplined in showing restraint against creature comforts. This dogma trickles into many aspect of Rim culture, for example, every meal the Raa family waits to eat once their food is served to show they are not slaves to their food.
They believe the Core is barbaric and has corrupted itself with a sense of entitlement, straying far from the Iron Gold's who conquered Earth bringing peace to Earth for the first time in her history. They view their focus on emulating the Iron Golds as an admirable goal. A goal they believe the Gold families of the Core are failing at.
"It's not what the ancestors intended. The Core-worlders are so desensitized to violence they've forgotten its to have a purpose. Violence is a tool. It is meant to shock, to change. Instead they normalize and celebrate it, and create a culture of exploitation where they are so entitled to sex and power that when they are told no, they pull a sword and do as they like." - Romulus au Raa 
It is likely that many Gold families of the Rim raise their children under strict rules of self-discipline. Lorn au Arcos of Europa wasn't raised in a palace like his Luna-born peers, but rather in a humble home outside of any city. His father believed in the denial of creature comforts, technology, and all other exorbitant aspects of Core culture (like cell-rejuvenation), and raised Lorn and his siblings with the same values.
Similarly, Romulus au Raa raised his seven children in his family's minimalist homes, with private tutors but no servants, surrounding them with educated conversations and an environment that discourages any sense of entitlement. His children were not allowed to watch holos before they turned 12-years old so that they could form their own opinions from their studies before they access the world.
Military aptitude is important to the Rim. They believe in following the ancestor's example in military prowess to reinforce their authority, as well as for the protection and advancement of their economy.
The Peerless Scarred leaders in the Rim smear the blood of their dead soldiers on their facial scar as a sign of respect.
Rim dwellers typically have paler skin, darker hair, and slightly larger eyes than Luna-borns. They are also very lithe with long jaws, "as though someone took the clay of their visages and pressed them with a vice". These characteristics are attributed to the fact The Rim is so far from the Sun and its stronger gravitational pull.
Rim architecture is very minimalistic and serene. The homes in the Rim that have been described all had peaceful gardens, with smooth stone, functional fruit trees, and calming features, such as fountains and wind chimes. The furniture is also simple and most surfaces are hard. Romulus au Raa is said to use an ancient Roman stone as a pillow. The homes were also described as seeming very clean and the spaces respected by its inhabitants. When Darrow and Mustang meet for negotiations at the home of Romulus au Raa, everyone present removed their shoes before entering.
"Odd seeing the boots of a dozen enemies stacked by the door. Like I've walked in on something very private." -- Darrow
The shipyards of Ganymede were first built in 497 PCE
Moon Lord Rebellions
Battle of Ilium
- Known Planets: Jupiter, Saturn, Uranus, Neptune, Pluto
- Known Moons: Io, Europa, Ganymede, Callisto, Sinope, Thebe, Titan, Rhea, Iepatus, Triton
- Kuiper Belt
It is a crime to own mirrors in the Rim. Mirrors are viewed as a device that will promote the obsession of oneself.
Rim Golds on Io have a blend of Japanese and South African ancestry. 
- Red Rising - chapter 9
- Golden Sun - chapter 27
- Red Rising - chapter 15
- Iron Gold - chapter 36
- Morning Star - chapters 40-41
- Morning Star - chapter 41
- Golden Son - chapter 28
- Iron Gold - chapter 26
- Iron Gold - chapter 22