Sy Myrth/Legends

Sy Myrth, formerly known as Far Barseg, was absorbed into Xim's empire as he expanded his borders from the Kingdom of Cron.

Sy Myrth was a member world of the Galactic Republic represented in the Galactic Senate by Toonbuck Toora until the planet seceded in 23 BBY. It was a founding world of the Confederacy of Independent Systems. The planet was later represented in the New Republic Senate.

Behind the scenes
According to Leland Chee's "Ask Lobot" article in Star Wars Insider 101, "There has been some suggestion that the Toonbuck Toora we see on Geonosis was actually a Shi'ido shape-shifter involved in a duplicitous ploy to bring Sy Myrth to the Confederacy. In that scenario, the plot is ultimately foiled, leaving the planet firmly loyal to the Republic." If this scenario is made canon, the HNN stories of the planet seceding will have to reflect an untrue rumor in-universe.