What is the main conflict in Dune Messiah by Frank Herbert?

Dune Messiah by Frank Herbert continues the cosmic drama of Dune, taking up the action in the frustrating twelfth year of the Emperor Paul Atreides' reign. It follows a treasonous plot that fails to overthrow him but leaves him blind physically and psychically, walking off into the desert and timeless immortality as the "Muad'dib."