They had converted to the Church of the East (Nestorianism) in the early 11th century and are one of the possible sources of the European Prester John legend.

[7][8] One common theory sees the name as a cognate with the Mongolian хар (khar) and Turkic qarā for "black, swarthy".

[9] According to the early 14th-century work Jami' al-tawarikh by Rashid-al-Din Hamadani, Mongol legend traced the clan back to eight brothers with unusually dark faces and the confederation they founded.

[14] The Keraites consisted of eight Mongolic tribes, including the Khereid, Jirkhin, Khonkhoid, Sukhait, Albat, Tumaut, Dunghaid, and the Khirkh.

A section is dedicated to the Keraites by Rashid al-Din Hamadani (1247–1318), the official historian of the Ilkhanate, in his Jami' al-tawarikh.

The "outer" faction was composed of tribes that pledged obedience to the khan, but lived on their own tribal pastures and functioned semi-autonomously.

The "capital" of the Keraite khanate was a place called Orta Balagasun, which was probably located in an old Uyghur or Khitan fortress.

[citation needed] After Kurchakus Buyruk Khan died, Ilma's Tatar servant Eljidai became the de facto regent.

Genghis Khan married the oldest niece of Toghrul, Ibaqa, and then two years later divorced her and had her remarried to the general Jürchedei.

[citation needed] Rinchin protected Christians when Ghazan began to persecute them but he was executed by Abu Sa'id Bahadur Khan when fighting against his custodian, Chupan of the Taichiud in 1319.

He attributes this to the lack of teachers of the faith, power struggles among the clergy and a willingness to make doctrinal concessions to win the favour of the Khans.

The legend of Prester John, otherwise set in India or Ethiopia, was also brought in connection with the Eastern Christian rulers of the Keraites.

In some versions of the legend, Prester John was explicitly identified with Toghril,[16] but Mongolian sources say nothing about his religion.

[23][24] According to these accounts, shortly before 1007, the Keraite Khan lost his way during a snowstorm while hunting in the high mountains of his land.

Yohannan replied to Abdisho telling him one priest and one deacon was to be sent with altar paraments to baptize the king and his people.

As a result of the mission that followed, the king and 200,000 of his people were baptized (both Bar Hebraeus and Mari ibn Suleiman give the same number).

[12][25] After the final dispersal of the remaining Keraites settling along the Irtysh River by the Oirats in the early 15th century, they disappear as an identifiable group.

[27] Kipchak groups such as the Argyn Kazakhs and the Kyrgyz Kireis have been proposed as possibly in part derived from the remnants of the Keraites who sought refuge in Eastern Europe in the early 15th century.