In its long progress to Mosul, Jerusalem, Rome, etc., the story of Prester John evaporated in a monstrous fable, of which some features have been borrowed from the Lama of Thibet, (Hist. Genealogique des Tartares, P. ii. p. 42. Hist. de Gengiscan, p. 31, etc.,) and were ignorantly transferred by the Portuguese to the emperor of Abyssinia, (Ludolph. Hist. Aethiop. Comment. l. ii. c. 1.) Yet it is probable that in the xith and xiith centuries, Nestorian Christianity was professed in the horde of the Keraites, (D'Herbelot, p. 256, 915, 959. Assemanni, tom. iv. p. 468 - 504.)