Avalokiteshvara or Chenrezig (tib. སྤྱན་རས་གཟིགས་) is a bodhisattva who embodies compassion of all Buddhas. He is the karmic deity of Tibet, and also one of the eight Bodhisattvas or spiritual sons of Buddha. He appears in different forms such as the thousand-armed and the thousand eyed, eleven-faced, and others. In Tibet there are many kings and masters who are manifestation of Avalokiteshvara. For example, king Songtsen Gampo, Dromtonpa, Dalai lamas, etc.
According to the legend, Avalokiteshvara made a commitment in front of Buddha Amitabha, would not rest until he had liberated all the beings in all the realms of suffering. After working diligently at this task for a very long time, he looked out and realized the immense number of miserable beings yet to be saved. Seeing this, he became extremely sad and his head split into thousands of pieces. Amitabha Buddha put the pieces back together as a body with very many arms and many heads, so that Chenrezig could work with myriad beings all at the same time.