According to Chapter 10, what is the role of a Sadguru, and how can they influence a devotee's life and destiny?

Chapter 10 explains that the Guru is the one eternal God, while all other gods are illusory. By placing pure faith and devotion in the Sadguru's feet, a devotee can have their fate changed, as the Guru "strikes a nail over the lines of destiny." When the Sadguru becomes the boatman, as described in this chapter, devotees can cross the three types of miseries—physical, mental, and divine—and the entire ocean of existence (Bhavasagar). Through the Guru's sight, the knots of the heart are broken, attachments vanish, and accumulated and current karmas are destroyed, leading to the effortless attainment of liberation.