According to the opening verses of this chapter, what is the nature of the Sadguru and His role for devotees?

The beginning of Chapter 18 extols the Sadguru as the "supreme Eternal one" and the "Truth of Brahman." He is hailed as the "Ruler of Maya" who, through experience, reveals the illusory nature of the world. For devotees, the Guru's crucial role is to make the divine accessible. As the chapter states, the Unperceivable One, which the Vedas and Shrutis debate endlessly, the Guru "point[s] out with a finger, effortlessly, to Your devotees." He is the ultimate teacher of the knowledge of the Self.