Rion, a planet with several moons orbiting it, was situated within the Outer Rim Territories of the galaxy. During the High Republic Era, the Skembo named Ceeril held the position of ambassador representing Rion. The human Jedi, Kanan Jarrus, and the Twi'lek pilot, Hera Syndulla, spent some time together on Rion's moons in the early years of the Galactic Empire's reign. Later, Jarrus was reminded of his time spent on Rion's moons while sharing Spiran caf with Syndulla aboard the Ghost, a VCX-100 light freighter. Following the Battle of Yavin, the Rebel Alliance dispatched the Millennium Falcon to the planet on a mission to acquire supplies from Razian. Han Solo nearly jeopardized the entire operation when he entered a Rion Swoop race.
The planet Rion was initially referenced in canon within the trivia gallery on StarWars.com for the Star Wars Rebels episode "Out of Darkness." Its first appearance was in "Swoop Racers," a comic penned by Cavan Scott, with illustrations by Derek Charm, and published in Star Wars Adventures (2017) 21 on May 8, 2019.
Within the Star Wars Legends narrative, the original concept of Rion came from The Second Kessel Run, a comic strip that appeared in 1980 newspapers, authored by Archie Goodwin and with art by Russ Manning.