This is the story of sheshnaag and ksheer sagar. sheshnaag who is all mighty himself and ksheer sagar who is the princess of vaikuntha, sheshnaag who consider himself slave of lord vishnu and ksheer who is the heart of vishnu.Sheshnaag is like a blazing fire and ksheer is rain which can calm any kind of fire down. Purpose of their birth is different. Sheshnaag is born to end the universe during pralay and ksheer is born to restart the universe after pralay.