One of the many local 'underworlds' - this time for the ancient Egyptians. Once considered to be situated west of the Nile Duat eventually ended up 'underground' much like the Christian Hell.
The hieroglyph for Duat is a star. Dead souls are brought here by Anubis to be judged in a court of the gods. Osiris sits as the judge.
See Egyptian Mythology for the otherworldly details...