Khu

Khu is generally associated as the combination of the Ka (Spirit) and Ba (Soul). The Ba being what makes a person unique similar to personality and teh Ka being the "life force" (for a lack of better words). The Ka is what distinguishes those alive from those dead. The understanding that the individual is not an individual at all but rather a “boundary” (for lack of better words) of totality is what is often referred to as the Khu, soul or spirit.

Aleister Crowley wrote in "The Law is for All": This 'star' or 'Inmost Light' is the original, individual, eternal essence. The Khu is the magical garment which it weaves for itself, a 'form' for its Being Beyond Form, by use of which it can gain experience through self-consciousness, as explained in the note to verses 2 and 3. This Khu is the first veil, far subtler than mind or body, and truer; for its symbolic shape depends on the nature of its Star.

Sources: http://en.wikipedia.org/wiki/Egyptian_soul - http://www.egyptiandreams.co.uk/egyptian-soul.php