What is the theme in Chapterhouse: Dune by Frank Herbert?

Religion is a major concern in all Frank Herbert's Dune novels, and Chapterhouse: Dune has its share. The Bene Gesserit's cynical "Missionaria Protectiva" is up to its old tricks, designing a religion around Sheeana, the Dune waif who controls worms in Heretics of Dune, and is now a Reverend Mother waiting for these children of the Divided God to appear in the new deserts of Chapterhouse. Sheeana sees how she could be the fulcrum to move the world, but events move too swiftly, and she flies away to an unknown universe, to whatever destiny awaits her.