Sian Tevv served as a councillor representing Sullust, a planet, and aligned himself with the Rebel Alliance during the Galactic Civil War. Information regarding Tevv reached the Imperial Ninety-Seventh Stormtrooper Legion when it was suspected that the local Cobalt Laborers' Reformation Front protesters were seeking connections with the Alliance. Prior to the Battle of Endor in 4 ABY, when the Alliance utilized Sullust as a staging location, Admiral Gial Ackbar assured Tevv that the rebels would ultimately liberate his planet. Sullust was subsequently liberated, following which Ackbar and Commander-in-Chief Mon Mothma accompanied Tevv to his inauguration.
During the Galactic Civil War fought between the Galactic Empire and the Rebel Alliance, Sian Tevv, a councillor from the Outer Rim Territories planet of Sullust, became a member of the Alliance. In 3 ABY, a clandestine Alliance cell known as the Sullustan resistance operated within Pinyumb, the capital city of the planet. After suspicions arose that the local protest movement, the Cobalt Laborers' Reformation Front, was attempting to establish links with the Alliance, the command structure at Sullust's Imperial garrison provided members of the Imperial Ninety-Seventh Stormtrooper Legion with details on rebels known to have connections with Sullust. This included Tevv, alongside Nien Nunb and Corjentain Malaqua, who were both members of the Sullustan resistance.
In 4 ABY, the Alliance fleet strategically used Sullust as a staging area before attacking and destroying the Empire's second Death Star above the moon of Endor. Admiral Gial Ackbar officially pledged to Commander-in-Chief Mon Mothma that the Alliance would liberate Sullust from Imperial control. This pledge was documented by archivist Hendri Underholt in The Rebel Files, a collection of non-electronic records. Ackbar's promise was followed by months of intense conflict, ultimately resulting in the liberation of Sullust. Subsequently, Ackbar and Mothma escorted Tevv to the governmental center for his formal inauguration ceremony.
Sian Tevv's initial mention in Canon occurred in the 2015 novel Battlefront: Twilight Company, penned by Alexander Freed. Tevv's origins lie within Star Wars Legends, where he was first referenced in Heir to the Empire Sourcebook by Bill Slavicsek, published in 1992 by West End Games for Star Wars: The Roleplaying Game. He later made an appearance in the 1996 novel X-Wing: Wedge's Gamble, authored by Michael A. Stackpole and serving as the second book in the Star Wars: X-Wing series.