According to Chapter 16, what is the fundamental nature of a Sadguru and why does He interact with devotees?

Chapter 16 describes the Sadguru as fundamentally being "Aptakama," meaning one whose desires are already fulfilled, and as an ocean of Truth, Consciousness, and Bliss. Despite needing nothing, He interacts with devotees for their own spiritual upliftment. The chapter explains that He has taken a body for the sake of helping others and uplifting the poor and lowly. He fulfills the devotee's desire for service and in doing so, makes them desireless. As Chapter 16 mentions, the Sadguru sometimes dons the "cloak of ignorance" to impart knowledge to the ignorant, giving sweet instruction without transgressing boundaries of conduct. His interactions are solely for the benefit of the devotee.