From wikipedia:Thirty-five hundred years have passed since Paul Atreides had become the messiah of the Fremen and the Emperor of the known universe at the end of the novel Dune. His son, Leto Atreides II, sees the path that his father Muad'Dib had also seen, a future that secures the continuation of human life throughout the universe. That future, however, requires an aberrant act of selflessness: becoming a hybrid of man and sandworm. At the end of Children of Dune, Leto II accepts this mantle of godhead from the Fremen and transforms himself into a monster of the desert, a sandworm, that will dominate the ecology of the planet Arrakis (known as Dune) for millennia. This is an act his father had been unwilling to do. Leto essentially accepts the terrible price of saving humanity which his father had rejected. God Emperor of Dune chronicles Leto's attempts to consummate the Golden Path, which delivers the volition of humanity by scattering it beyond the perceived safety of the Imperium's known universe, and also by destroying the possibility of the Imperium's control by any single entity, including himself.