八思巴文
Kublai invited lama Drogön Chögyal Phagpa of Sakya school of Tibetan Buddhism to spread Buddhism throughout his realm (the second introduction of Buddhism among the Mongols). Buddhism became the "de facto" state religion of the Mongol Yuan state. In 1269, Kublai Khan commissioned Phagpa lama to design a new writing system to unify the writing systems of the multilingual empire. The 'Phags-pa script, also known as the "Square script", was based on the Tibetan script and written vertically from top was designed to write in Mongolian, Tibetan, Chinese, Uighur and Sanskrit languages and served as the official script of the empire.