Yelü Dashi
Before Tianzuo launched his ill-fated offensive, a member of the royal family, Yelü Dashi, advised him not carry out the expedition. Upon Tianzuo's refusal, Dashi abandoned the emperor's camp and fled northward. From there he was able to eventually set up his own domain and expand west, forming the successor state known as the Qara Khitai or Western Liao.