According to Chapter 18, what are some of the supreme qualities attributed to the Sadguru?

Chapter 18 opens with powerful salutations that describe the supreme nature of the Sadguru. He is hailed as the supreme Eternal one, the very Truth of Brahman, and the Ruler of Maya who can show the world to be an illusion. The text further describes the Guru as being without beginning or end, beyond duality, and free from any blemish. As stated in this chapter, the Sadguru is presented as the ultimate teacher of the knowledge of the Self, capable of revealing the "Unperceivable One" that even the Vedas and Shrutis endlessly debate.