Yin Mountains
Little is known about Helian Duo's background, including his birth year, other than that, as of the time of Emperor Yizong, he was then a Tuyuhun chief and carried the Tang-bestowed title of commandant of Yin Mountains. Later, when Tang imperial forces had to battle a rebellion led by Pang Xun at Xu Prefecture (徐州, in modern Xuzhou, Jiangsu), Helian participated in the campaign.