元朝秘史
According to a legend narrated by "The Secret History of the Mongols", a Mongol woman named Alan Gua had a son, named Bodonchar, some years after her husband has died. She claimed a radiant yellow person visited her at night and impregnated her. She believed the visitor was the god Tengri. Bodonchar became the founder of the Borjigin tribe and a direct ancestor of Genghis Khan.