Genghis Khan wrote to and spent much time with Qiu Chuji one of the Seven Taoist Immortals (Sages) who was the founder of the Dragon Gate sect (lóngménpài 龍門派) of the Complete Reality School (全真派) of Taoism. The incredible description of their correspondence and meeting is in "The Travels of Ch'ang Ch'un to the West, 1220-1223"
Genghis Khan / Temüjin Borjigin
Qiu Chuji as painted by Guo Xu, 1503