Chapterhouse is the planetary base of operations of the Bene Gesserit Sisterhood in Heretics of Dune, over 5000 years after the events of Dune (when the Bene Gesserit Mother School had been located on Wallach IX). After the dreaded Honored Matres destroy the desert planet Rakis – the only known source of the all-important spice melange – the Bene Gesserit begin to terraform the surface of green Chapterhouse into a desert in order to breed and begin a new life-cycle of sandworms and renew the spice cycle under their own control. Hiding from the dreaded Honored Matres, the Bene Gesserit keep the location of Chapterhouse secret and shield the planet behind a wall of no-ships, spaceships invisible to long-range detection instruments and hidden from the power of prescience.
Read more about this topic: List Of Dune Planets