How does Chapter 18 characterize the Sadguru and the nature of the knowledge He imparts?

Chapter 18 extols the Sadguru as the 'supreme Eternal one,' the 'Truth of Brahman,' and the 'Ruler of Maya.' He is described as being beyond duality, without blemish, and both beginningless and endless. The chapter emphasizes that the Guru is the ultimate teacher of the knowledge of the Self. This knowledge is not complex; the Sadguru effortlessly points out the 'Unperceivable One,' the very subject that the Vedas and Shrutis debate endlessly. He shows the true path to each person according to their worthiness, without creating intellectual conflict, making profound spiritual truths accessible to His devotees.