By the Liao 遼 called Zubu 阻卜. The Kereyid were one of the mightiest peoples of the Mongolian steppe before the Mongol federation swallowed them. The question if the Kereyid belong to the Turkish or to the Mongolian branch of the Altaic peoples is not solved yet. During the Liao period 遼 the Kereyid were subjected and controlled by the Northwestern Bandit Suppression Commission (Xibei zhaotaosi 西北招討司). Nestorian Christianism was widespread among the Kereyid. In 1092 the Kereyid rebelled against the Liao domination but was defeated some years later. The Kereyid ruler "Hurjahus Beilu Qaghan 忽兒札胡思盃祿汗" was victorious against the Merkit and Tatar. His son Toghril (Tohoril) "Tuoli 脫里", defeated by his uncle, sought for help by the Mongol chieftain Yesügai 也速該, the father of Genghis Qaghan. The relation between the two contributed to the development of the federation between the Kereyid and the Mongols, and the Kereyid became the main force of the Mongolian high plateau challenging the domination of the Jin Dynasty 金 in northern China and the Naiman federation in the west. In 1203 Toghril (Royal Qaghan Wanghan 王罕) attacked Genghis Qaghan who had become stronger and stronger, and defeated the Mongol ruler. But Genghis was strong enough to reunite his forces and to destroy the Kereyid, Toghril fled and was killed by the Naimans, his son Yilahe Sangkun 亦剌合桑昆 was murdered in Kucha (Turfan/Xinjiang). The person of the Royal Qaghan can be recovered in the legend of the priest king John in Central Asia that was widespread in Middle Age Europe. The people of the Kereyid federation were incorporated into the Mongol union, and many people of high rank during the Mongol reign and the Yuan Dynasty 元 were Kereyid, for example the mother of Khubilai Qan, "Suolu Hetieni 唆魯禾帖尼".