Xerxes was the ruler of Argos. He inflicted his townspeople with heavy taxes and ruled with an iron fist, provoking a number of villagers to form the Black Wolf Pack, led by Flora. Not happy with the rebellion of his townspeople, he ordered them to reveal the identity of their leader: failing to do so forced him to throw them all in prison until their leader is presented.
When Xena learns that one of her friends, Flora, is involved with the Black Wolves, she decides to create a false alliance with Xerxes to uncover the identity of the Black Wolf, however her true intentions was only to free Flora. She manages to free the Wolves (and Flora who happened to be the leader) and kills Xerxes in combat.