A missionary to a leader of this ethnic group designed the Phags-pa script.
This ethnic group traditionally divided winter into nine sets of nine days known by descriptive phrases such as "the tail of a 3 year old ox freezes and falls off". Because these people regard fire as sacred to the divine Qurmusata King, it is taboo to stamp out or douse a fire within their dwellings. Many religious sites among these people feature a heap of stone or wood called an ovoo. Sacred sports called danshig are played at the yearly Naadam festival of this ethnicity, whose traditional pantheon consists of 99 (*) sky spirits.  A missionary to a leader of this ethnic group designed the Phags-pa script. It is believed that these people's near-total religious toleration was once enshrined in a secret law code called the Yassa.  For 10 points, name this ethnicity whose nation ended atheistic Communist rule in 1990, and which has since seen revivals of Buddhism, Tengriism, and shamanism.
This ethnic group traditionally divided winter into nine sets of nine days known by descriptive phrases such as "the tail of a 3 year old ox freezes and falls off".
Mongols [or Mongolians; prompt on Turkic peoples]