Duat

Is the Egyptian idea of the underworld (also called Akert, Amenthes, or Neter-khertet). To the Egyptians, the underworld was divided into sections filled with dangers that the Egyptian Soul had to pass through. This is the same realm that Ra was believed to pass into each night and battle Apophis. The Egyptian Underworld is described in many funerary texts that are found in tombs of mummies, believed to help guide them through death.
Duat is where the famous "Weighing of the Heart" is displayed. Where the soul, shown as a heart, is weighed on the scales of Anubis against the feather of Ma'at. Ammut was believed to eat the souls of the people whose heart did not match the exact weight of Ma'at's feather. It was thought that the heart itself was then eaten by a lion. 
The Egyptian idea of the underworld influenced many other ideas of afterlife in other cultures.