What is the fundamental nature and role of a Sadguru as explained in the teachings of Chapter 16?

As detailed in Chapter 16, the Sadguru is described as being 'Aptakama,' meaning one whose desires are always fulfilled, thus needing nothing from a disciple. His primary role is to fulfill the disciple's desire for service and ultimately make the disciple desireless. He is an ocean of Truth, Consciousness, and Bliss. The chapter states that the Guru takes on a physical body for the sole purpose of helping others and uplifting the poor and lowly. Donning a cloak of ignorance, He imparts knowledge to the ignorant and provides sweet instruction, guiding the devotee towards union with Brahman.