What is the setting of Chapterhouse: Dune by Frank Herbert?

Picking up where Heretics of Dune ends, 1,500 years after the death of the God-Emperor Leto II "the Tyrant," Chapterhouse: Dune examines the Bene Gesserit Sisterhood with its back to the proverbial wall, in frantic survival mode. The hysterical Honored Matres are harrying them at every turn, and have reduced the number of Bene Gesserit planets to a handful. Chapterhouse is emptying as Sisters with worms and minimal melange supplies are sent into a new Scattering, made all the more worrisome by the fact no Sister ever returned from the first Scattering. During the novel, the planet is seen undergoing a conversion into desert so it can support the offspring of the great sandworms of Dune. The hubris of changing an entire planet is examined at length.