Have you heard of the Great Pacific Garbage Patch? Well, welcome to the Great Galactic Garbage Patch, also known as Salva.
Space is a big place, and a big place contains a lot of trash. A lot of this is in interstellar space: ejected waste, lost cargo, abandoned spacecraft, the losers of battles, spent fuel stages, and all manner of wayward junk.
Due to a quirk of galactic gravitational fields, a large swath of the galaxy has it's interstellar objects funneled into a singular location: a humble, nameless system, devoid of habitable planets and far remote from the nearest civilization. It's here that all this garbage began to accrete, swirling up into a sphere of a size somewhere between Mercury and Mars.
Salva is a planet shaped like a pile of garbage. Flat plains are scarce, with most of the surface being trash heaps and rough terrain with chasms that can run for miles below the surface. The planet's innards are much the same: space debris, crushed down by gravity into a semisolid metamorphic slurry, surrounding a core of solid metal.
The first inhabitants of Salva were refugees, crewmembers of ships left adrift by engine failure or loss of power. These ships were drawn to Salva and became part of the planet, serving as sites for the first cities.
Future generations of Salvans would operate much in the same way that their ancestors did: scouring the wastes for useful materials that could be repurposed to help them stay alive. Salvan Creole is a heterogeneous mix of dozens of languages, with particular dialects spoken by the descendants of different crews.
Cities were built wherever flat (preferably level) surfaces could be found: atop the hulls of freighters, or on areas artificially cleared of junk. The largest cities have populations sometimes reaching into the low five-digit range, although rural settlements generally consisted of only a few families.
The hallmark of a major city is its smooth, clean, shiny ground surface, full of ramps and elevators to emphasize their flat planes. The condition of your floor is a major signifier of status on Salva. While most material wealth is available in abundance for anyone with the will to retrieve it, a well-polished floor is available only to those with the manpower to maintain it.
For this reason, the larger Salvan cities contain disproportionately high volumes of people with mobility-related disabilities. A standard Earth wheelchair would work just fine (possibly even better, due to the abundance of ramps) in Salvan cities. In smaller towns or villages, however, the ground is rougher and more treacherous. In such cases, wheelchairs might be modified to use treads or hover technology, while in the roughest of cases, only walking exo-suits would suffice. For these reasons, a significant amount of rural disabled people flock to cities, establishing support networks and helping others make the trek.
Deep in the wastes, far from the cities and towns, a galaxy's worth of discarded technology, chemicals, biological samples, organic matter, and other nasty substances mix and foment together for years. Out of such sludge rises Salva's "wildlife"; a mess of techno-organic monsters struggling in their own way to find food or fuel. Such creatures span the full spectrum from "chemically enhanced animal" to "literally just a robot" and every weird combination in between. Sightings of such monsters near settlements is rare, but some think these creatures are more than they seem.

