|Universe||Captain N Universe|
|Primary Terrain||Maximum Security Prison, Mineral Mines|
|Notable Species||Highly Variable|
RX338, nicknamed Prisonworld, is a planet that was converted in ancient times into a maximum security prison by the evil emperor Suimar. Originally it served as the location that he would place any rebels who might endanger his despotic rule. Here they were forced to perform manual labor in the planet's rich mineral deposits, which had been carved into mine shafts, curving deep into the planet.
When Suimar was eventually overthrown, the Galactic Federation took it over and used it to imprison the galaxy's most dangerous villains. There are now over 100 separate prison blocks, each designed to house and secure villains of any aptitude, from any world. It is surrounded by a chain of hunter killer satellites and space mines to prevent anyone from arriving or leaving the world, and the asteroid belt that encircles the oddly-shaped world is infested with Starsharks, making movement through its space all the more dangerous.
The Federation Police currently manage both the prisons as well as the prisoners here, yet have become somewhat corrupt, and while punishments include solitary confinement, they also include illegal beatings performed by the officers.
- It is highly likely that RX338 was named after SR388, as the Captain N universe includes much references to the Metroid universe.