Yelü Chucai was a retainer of which founder of the Mongol Empire?
Yelü Chucai:  He was the first of Genghis Khan's retainers to formulate policy during the Mongol conquests, and he also introduced many administrative reforms in North China during the reign of Genghis Khan and his successor Ögedei. Genghis Khan: Genghis Khan (c. 1162 August 18, 1227), born Temüjin, was the Great Khan and founder of the Mongol Empire, which became the largest contiguous empire in history after his death.
Genghis Khan