Book of Gates
What is known of the "Duat" derives principally from funerary texts such as the "Book of Gates", the "Book of Caverns", the Coffin Texts, the Amduat, and the "Book of the Dead". Each of these documents fulfilled a different purpose and give a different conception of the "Duat", and different texts could be inconsistent with one another. Surviving texts differ in age and origin, and there likely was never a single uniform conception of the "Duat", as is the case of many theological concepts in ancient Egypt.