According to Chapter 10, what is the role and significance of a Sadguru for a devotee?

Chapter 10 profoundly explains the significance of the Sadguru, or true Guru. It states that the Guru is the one eternal God, while other gods are illusory. By placing faith in the Guru's feet, a devotee can change their destiny, as the Guru 'strikes a nail over the lines of destiny.' The chapter further elaborates that the service of the Sadguru destroys the worldly existence (Samsara) and helps devotees cross the three types of miseries. Just as one needs a boatman to cross an ocean, one needs a Guru to cross the ocean of existence (Bhavasagar), ultimately attaining liberation and bliss effortlessly.