Tibet was once a strong power contemporaneous with Tang China (618–907). Until the Tibetan Empire's collapse in the 9th century, it was the Tang's major rival in dominating Inner Asia. <answer>The Yarlung rulers of Tibet</answer> also signed various peace treaties with the Tang, culminating in a treaty in 821 that fixed the borders between Tibet and China.
Who signed multiple peace treaties with the Tang? 
The Yarlung rulers of Tibet