Based on Chapter 12, what is the fundamental nature and ultimate purpose of a Sadguru like Sai Baba?

According to the teachings in Chapter 12, the Sadguru's fundamental nature is being one with the divine, an embodiment of 'Truth, Consciousness, and Bliss' who is inseparable from the Supreme Soul. The ultimate purpose of such a master is to guide souls across the worldly ocean. The text poetically describes the Sadguru as the 'Agastya... for the ocean of worldly existence' and the 'sun for the darkness of ignorance.' His purpose is to remove the 'obsession with duality' from the minds of all, even the 'dull-witted,' and to incarnate for the sake of His devotees, helping them overcome any obstacle on their spiritual path.