Quick recap
Leto II, half human and half sandworm, has ruled as a tyrant for 3,500 years. He controls all the spice, has dissolved the Landsraad and replaced the Fremen army with an all-female guard that obeys him blindly. At his side is yet another Duncan Idaho ghola, one of many over the millennia. Leto falls for Hwi Noree, the Ixian ambassador, even knowing she was made to seduce him. Siona Atreides, leader of a rebellion, joins Duncan to kill him. During the wedding procession they bring down a bridge and Leto falls into the river; the water tears him apart, and the sandtrout in his body scatter. Before dying, he reveals that Siona is invisible to prescience. Duncan and Siona are left with the empire.

