Rios is a primarily agricultural world in the Southeast corner of human space. Eight hundred million humans call the planet home as of 2265.
The planet was a former Katarn world first settled by humans in 2208 after the Bugs who had wiped out its original Katarn inhabitants were themselves wiped out in turn by theTech Infantry. The Katarn had terraformed the planet to their liking, and it did not take much effort for humans to tweak the environment to produce large areas of good farming conditions.
Rios remained under the control of the Grand Council in the early stages of the Third Civil War, but the system was invaded by the Jurvain in March of 2243. After the Jurvain battle fleet entered the system and deployed for battle, the entire Jurvain landing force was destroyed behind them when the Ashdown jumpgate they were passing through was destroyed by Captain Erich Von Shrakenberg. However, his jubilation was short-lived, for almost immediately a second fleet jumped in from New Madrid, but this fleet was loyal to the Tech Infantry Rebel faction of "Auntie Sarah" Dunmeyer. As the Jurvain fleet closed in on Von Shrakenberg's cruiser, the EFS Schaumburg, he led them on a high-velocity chase on a slingshot trajectory around the system primary. Several Jurvain ships were damaged or destroyed when they unsuccessfully tried to cut inside the Schaumburg on the turn and entered the stellar corona. The Schaumburg itself was badly scorched, losing half its point defense mounts in the process. Curving back out from the star, the Schaumburg led the Jurvain fleet directly towards the ongoing space battle being fought between the rebel and loyalist fleets, and as they passed the disabled hulk of the Loyalist fighter carrier EFS Varyag, the Schaumburg fired upon the hulk with its Particle Cannons set for gluon streams. These set off a fusion chain reaction in the deuterium and hydrogen fuel tanks aboard the Varyag, turning it into a gigantic explosive mine, and the ensuing explosion wiped out most of the pursuing Jurvain fleet. The few surviving Jurvain ships were easily mopped up by the victorious Rebel task force, which went on to occupy Rios for the following year. Rios surrendered to Arthur Clarke's forces in April of 2244, and later served as the jumping-off point for Clarke's conquest of the Jurvain. Rios also remained loyal to the Earth Federation during the Ascension War, but was peacefully absorbed into the Holy Terran Empire early in 2266.