Who is Tang Wenting / Bill Tang from Dragon Bones: A Novel and what is their importance?

Tang Wenting (Bill Tang) is Xiao Da'd right hand man. He uses a situation at the meeting where Hulan saves a little girl's life as a weapon against her, and against the Chinese government. Tang attempts to kill David, as well as Stuart Miller, in an effort to obtain the ruyi. In the end, Tang is captured.