The Duat, is the Egyptian realm of the dead.
Mummy: the ResurrectionEdit
Mummies and their allies use "Duat" as another name for the Underworld, where every mummy's ba soul spends a certain amount of time between resurrections. Specifically, it refers to the Dark Kingdom of Sand, which was once ruled by Osiris; after the Sixth Great Maelstrom, most of this Dark Kingdom is engulfed in a brutal sandstorm, but A'aru remains protected by Anubis and the Judges of Ma'at. 
Vampire: the MasqueradeEdit
To the Followers of Set the Duat is the afterlife, thought of as a mirror to the living world. What physically exists in life, also exists in Duat, which is why people are burried with their possessions.