What is the 'causal body' and what is its role in the spiritual path?

As described in Chapter 50, the 'causal' (karana) body of the soul is also known as the 'Unmanifest' (Avyakruta). It is described as having the reflection of consciousness and being the very cause of pure ignorance. It is the deepest layer of conditioning that veils the soul's true nature. Its role in the spiritual path is that of the primary obstacle to liberation. The text states that the removal of this causal body is essential for Moksha. This removal is not a physical act but a metaphysical one, accomplished only through the dawning of the knowledge of the unity of Brahman and the Soul, which directly dissolves the ignorance that constitutes this body.