Based on Chapter 19, what is the true nature of the Soul, and how is it distinguished from illusion and the ego?

Chapter 19 delves deep into the nature of the Soul, describing it as self-luminous, pure consciousness, changeless, and formless. To explain how this pure Soul interacts with the world, the chapter uses the analogy of a crystal, which appears to take on the color of a nearby object but remains intrinsically pure and distinct. This is contrasted with the false ego of identifying with the body ('I am the body'), which is described as an illusion, similar to mistaking a coiled rope for a snake. The Soul is distinct from the body, senses, and mind, remaining untainted by the superimpositions of Maya.