Between 19 BBY and 18 BBY, it was not under the control of the recently formed Galactic Empire. At that time, Clone Force 99 members Tech, Wrecker, and Omega, as well as information broker Ciddarin Scaleback, arrived at the planet via a Star Commuter 2000 to meet Cid's droid racer, TAY-0. Cid later made a bet with the Dowutin crime lord Grini Millegi that TAY-0 would win the next race. However, Nosaurian racer Jet Venim won the race. Unable to pay, the members of the Bad Batch stepped up and instead made a new deal of paying double if they lost in the next race. With TAY-0 gone, Tech became the racer for Cid and won the race, thereby saving Cid from Millegi.
Serolonis was a desert planet which featured mainly sand dunes and rocky terrain. From space, it looked like a reddish-yellow ball with patches of green. At least one settlement was on the planet, the main attraction of which was the Safa Toma Speedway, a racecourse with where people could watch Riot Racing, a sport popular on the planet. By 18 BBY, the world was host to various criminals, smugglers, and gamblers.
Serolonis first appeared in the Star Wars: The Bad Batch episode "Faster." The planet is named after legendary Italian director Sergio Leone, and was originally created for an unfinished arc of Star Wars: The Clone Wars featuring Cad Bane and a young Boba Fett. While The Bad Batch episode's StarWars.com trivia gallery spells the planet's name as "Serolonis," the concept art gallery for the same episode renders the name as "Seralonis."