For what purpose did Sai Baba appear in Shirdi, and what happened when this purpose was fulfilled?

According to Chapter 43, Sai Baba appeared in Shirdi for the sake of his devotees' protection, drawn by their collective past merits and devotion. He manifested from an unmanifest form to fulfill this purpose. When this task for the devotees was considered over, he chose to leave his body. However, as Chapter 43 explains, this was not a conventional death. He could die at will and instead burned his body in the 'fire of Yoga,' merging himself back into the unmanifest. From this state, he continues to enjoy his true self and keeps his devotees spiritually awake, proving that his consciousness was never perishable.