The Yassa was the legal code of the Mongol Empire, and it was kept secret in order to maintain the power and authority of the ruling dynasty. The Yassa was primarily used to govern the behavior of the Mongol elite, including the ruling family and the aristocracy, and it was not made available to the general public.

In practice, the Yassa was administered by the Mongol rulers and their officials, who used it to set standards for behavior and resolve disputes within the elite. The Yassa was also used to regulate relations between the Mongols and the various subject peoples within the empire, and it was used to punish crimes and enforce the will of the rulers.

It is not clear how the secrecy of the Yassa affected the legal and civic culture of the Mongol Empire. It is possible that the secrecy of the code contributed to the perception of the Mongols as a harsh and authoritarian regime, but it is also possible that the code helped to maintain order and stability within the empire.

Overall, the Yassa was an important part of the legal and governance system of the Mongol Empire, and its secrecy helped to maintain the power and authority of the ruling dynasty.