The political, scientific, and social fictional setting of Herbert's novels and derivative works is known as the "Dune" universe, or Duniverse. Set tens of thousands of years in the future, the saga chronicles a civilization which has banned , referred in the saga as "thinking machines", but has also developed advanced technology and mental and physical abilities. Vital to this empire is the harsh desert planet Arrakis, only known source of the spice melange, the most valuable substance in the universe.