One important subordinate deity is Xuan Tian Shang Di, Supreme Emperor of Dark Heaven. The Jade Emperor dispatched him to Earth to battle a band of renegade demon-kings. His iconography shows him enthroned and using a serpent and a turtle—leaders of the demons—as a footstool. A legendary woman named Xi Wang Mu, also known as the Queen Mother of the West, figures prominently in some Daoist writings. She is a patroness of immortality, often depicted in the company of Jade Maidens, one carrying a fan and the other a bushel of the peaches of longevity. Ruling the East is her divine consort, Dung Wang Gong, who lives in the remote magical fastness of the Kun Lun mountains. In a reversal of the more usual dynamic, a “God of walls and moats,” also known as the City God, began as a popular deity and made his way into the Daoist pantheon. During certain periods in history, the Heavenly Master appointed a given city’s tutelary deity. City God has the assistance of several other figures, called “spirit secretaries,” in the idiom of public administration. They help the City God deliver his reports on the conduct of citizens to the authorities in Hell. A goddess named Dou Mu (Mother of the Bushel of Stars, or Northern Dipper) functions in Daoism much the way Guan Yin does in Buddhism, offering limitless compassion for the suffering. Some other potent beings are clustered in groups. The Sen Nin are a group of sacred figures who dwell in Heaven or in the distant misty mountains. Among the Sen Nin the most important are the Eight Immortals. Originally persons either historical (three) or legendary (five), they function as guardian figures of Daoism. Although they are not officially divine, popular lore sometimes attributes divine powers to them. They are called Later Heaven Deities, as are all human figures who eventually achieved immortality.