Sen Xiao Yun is an independant businesswoman who arose from obscure origins in Shanghai to become owner and operator of two notorious nightclubs on the East Coast of the United States, "The Serpent's Nest" in New York City and "The Little Serpent's Nest" in Boston. While nothing has ever been proven in a court of law, it is suspected that she holds has ties to several criminal organizations, and her clubs are nexus' for criminal activity, primarily prostitution, drugs, and the slave trade. She is rumored to have uncanny powers of persuasion, and an ability to eliminate witness' and evidence of her alleged criminal dealings. (In one famous case, a witness actually comitted suicide right on the witness stand of a New York Criminal Court.) Ms. Sen is a ruthless and opportunistic individual and her nickname, while publicly denied, is well earned in the underworld.

Recently, her establishment in Boston, "The Little Serpent's Nest" was destroyed in a bombing attack by a gang known as The Snowmen. The Jade Serpent was present at the time, but fled the scene shortly after B.A.S.E. agents infiltrated the establishment searching for Faceless Ling, who would resurface later as Nonentity. The B.A.S.E. operatives had been tipped off to the presence of this dangerous fugitive by an escaped worker from the club's "private section" who fled, her fear of the faceless killer overcoming her fear of her boss. B.A.S.E. bureau cheif, The Darkness, encountered The Jade Serpent she fled, and reports she used some form of magic or mental domination power to elude him, a fact corroborated by B.A.S.E. agent The Djinn, who also was affected by this mysterious power. Sen Xiao Yun has returned to New York City, and based on the above testimony, is now under surveillance by that city's B.A.S.E. chapter. Several cases may have to be re-opened in light of this individual's use of super powers.