Tibet retained nominal power over religious and regional political affairs, while the Mongols managed a structural and administrative rule over the region, reinforced by the rare military intervention. This existed as a "diarchic structure" under the Yuan emperor, with power primarily in favor of the Mongols. Mongolian prince Khuden gained temporal power in Tibet in the 1240s and sponsored Sakya Pandita, whose seat became the capital of Tibet. Drogön Chögyal Phagpa, Sakya Pandita's nephew became Imperial Preceptor of Kublai Khan, founder of the Yuan dynasty.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What did the Mongols retain nominal power over?
unanswerable