Dhrtarastra is the Heavenly King of the east and the God of music. His symbolic weapon is the lute(stringed instrument/琵琶). He is harmonious and compassionate and protects all beings. He uses his music and his lute to convert others to Buddhism. If a string is too tight, the music note would sound hard and dull, and the string can be broken easily. However, if a string is too loose, no sound can be produced. His instrument symbolizes that our attitude toward life and Buddhism should neither be over aggressive nor too relax. The best is to avoid being in any of the opposite sides but rather stay in the middle range.
In Buddhism, the Four Heavenly Kings are four gods, each of whom watches over one cardinal direction of the world.
The Four Heavenly Kings are said to currently live in the Caturmaharajika Heaven (Four Great Kings Heaven/四天王天) on the lower slopes of Mount Sumeru(須彌山), which is the lowest of the six worlds of the devas of the Kamadhatu (Realm of Desire/六欲天). The four Heavenly Kings are located at the north, south, east, and west sides of Mount Sumeru because they are the protectors of the four continents of our world: Purvavideha to the east(東勝神洲), Jambudvipa to the south(南瞻部洲), Aparagodaniya to the west(西牛賀洲), and Uttarakuru to the north(北俱蘆洲). They are also the protectors of the world and fighters of evil, and each can command a legion of supernatural creatures to protect the Dharma. They have a five-hundred-year lifespan, of which each day is equivalent to 50 years in our world; thus their total lifespan amounts to about nine million years in human calendar. All four serve Sakra(the Lord of the Devas/帝釋天) of Trayastrimsa(忉利天). On the 8th, 14th and 15th days of each lunar month, the Four Heavenly Kings either send out messengers or go themselves to see how virtue and morality are faring in the world of men. Then they report upon the state of affairs to the assembly of the Trayastrimsa devas.
They are vowed to protect the Buddha, the Dharma, and the Buddha's followers from danger.