Wikipedia
The Amduat (literally "That Which Is In the Afterworld", also translated as "Text of the Hidden Chamber Which is in the Underworld" and "Book of What is in the Underworld") is an important Ancient Egyptian funerary text of the New Kingdom. Like many funerary texts, it was found written on the inside of the pharaoh's tomb for reference. Unlike other funerary texts, however, it was reserved only for pharaohs (until the 21st Dynasty almost exclusively) or very favored nobility.
It tells the story of Ra, the Egyptian sun god who travels through the underworld, from the time when the sun sets in the west and rises again in the east. It is said that the dead Pharaoh is taking this same journey, ultimately to become one with Ra and live forever.
The underworld is divided into twelve hours of the night, each representing different allies and enemies for the Pharaoh/sun god to encounter. The Amduat names all of these gods and monsters. The main purpose of the Amduat is to give the names of these gods and monsters to the spirit of the dead Pharaoh, so he can call upon them for help or use their name to defeat them.
As well as enumerating and naming the inhabitants of the Duat (or Dwat) both good and bad, the illustrations of the 'book' show clearly the topography of the underworld. The earliest complete version of the Amduat is found in KV34, the tomb of Thutmose III in the Valley of the Kings.