(*)
Through duress, this state's founder was granted as a bride a foreign princess who introduced the cultivation of grains and rapeseed to his country. The assassination of Rapalcan allowed this state to be ruled by Langdarma, whose death would later spark this state's Era of Fragmentation. George de Roerich published the first English translation of a history of this state called the Blue Annals. During the An Lushan rebellion, this state won dominion over the Qiang people from the Tang dynasty. (*) Avalokiteshvara is thought to have been incarnated as the first of the three "Dharma Kings" to have ruled this state, a ruler named Songsten Gampo who introduced a variety of Buddhism that developed Red and Yellow Hat sects. For 10 points, identify this state whose rulers controlled Qinghai, Xinjiang, and much of its namesake region from Lhasa.
Through duress, this state's founder was granted as a bride a foreign princess who introduced the cultivation of grains and rapeseed to his country.
Tibetan empire (or Bod)