Leto II Atreides, the God Emperor, has ruled the universe as a tyrant for 3,500 years after becoming a hybrid of human and giant sandworm in Children of Dune. The death of all other sandworms as a result of the terraforming of Dune, and his control of the remaining supply of the all-important drug melange, has allowed him to keep civilization under his complete command. Leto has been physically transformed into a worm, retaining only his human face and arms, and though he is now seemingly immortal and invulnerable to harm, he is prone to instinct-driven bouts of violence when provoked to anger. As a result, his rule is one of religious awe and despotic fear.
