Toghrul Quan, and many of the Kerait people were Nestorians. So were Mongke, Qublai and Hulegu Quans’ mother, Sorghatani Beki, and Hulegu’s wife. The Nestorians made sizable inroads into western Asia, and may have spawned the ‘Prester John’ legend.
Kaifeng
Jesus Sutras
Christians in China: A.D. 600 to 2000
by Father Jean Charbonnier,
contributions by David Notley,
tr. by M. N. L. Couve de Murville