Atlas City is ruled by Duke Rithaln. The local currency is the leeb, worth 1/10 of a gold piece.
Atlas City is home to a Sorcerer's Guild, which was previously led by Halcyform the White. Following Halcyform's mysterious disappearance, infighting began between his two potential successors, Daymia the Blue and Tarim the Violet, with negative results for the city as a whole. By the end of the events of the fourth Slayers novel, Halcyform, Daymia, and Tarim are all dead, and it is unclear who will assume leadership of the local Sorcerer's Guild.
When Lina Inverse is first introduced in both the novels and the TV series, she is on her way to Atlas City.