What is the main conflict in God Emperor of Dune by Frank Herbert?

God Emperor of Dune describes the climax of the millennia-long "Golden Path" by which Leto II Atreides sacrifices everything and tyrannically prevents the extinction of humankind. The God Emperor Leto II is nearing the end of his anticipated 4,000-year lifespan and reign according to the "Golden Path." Siona Atreides, a beautiful rebel leader is the daughter of Leto's majordomo, Moneo. Hoping to find his vast stash of melange, she steals plans to Leto's citadel and journals that show he can be defeated through love.