S'Shah was the King of Serphidi and was loyal to the Galactic Empire. When S'Shah attained power, he modified the traditional Serphidi jousts into contests to the death called Doom-Jousts. Further, he declared that the only way he would relinquish power was if he were beaten in a Doom-Joust; many Serps tried but none succeeded.
When the Rebel pilots Luke Skywalker, Cinda Tarheel, and Berl arrived on Serphidi in an attempt to sway the Serps away from the Empire and towards the Rebellion, S'Shah and a fellow Serp, Chahis discovered and attacked them. In the battle, Berl was killed and Tarheel captured by the king and she was to be served as part of a meal at the banquet following the next Doom-Joust. Skywalker escaped capture, but they would meet again as the young Rebel challenged the king to a joust on behalf of Elglih, an elderly local who opposed S'Shah.
Skywalker bested the Serp king in the contest, and was forced to kill him as S'Shah refused to be taken alive. With the king dead, Elglih succeeded him since Luke declined the honor, and the new king pledged allegiance to the Rebel Alliance.