The events of the novel take place a full century after the beginning of the Butlerian Jihad, and are divided into two parts, the first beginning in the year 108 B.G. (before Guild) and detailing a biological war waged by the thinking machines on the humans. The second part of the novel begins in 88 B.G. and covers the events after the Great Purge, leading up to the fateful Battle of Corrin. At the conclusion of the Legends of Dune series, several story lines started in the previous two novels lead to the political and social climate that is well established in Frank Herbert’s original Dune series.
The Machine Scourge
The evermind Omnius is continuing with his plans to eradicate all humans in the universe. After first being suggested by the traitor Yorek Thurr, a RNA retrovirus is designed by the captured Tlulaxa Rekur Van and the independent robot Erasmus. Omnius then launches capsules containing the retrovirus to infect the planets inhabited by the hapless humans. With a 43% direct-mortality rate, the virus succeeds in effectively crippling the League of Nobles, leaving them vulnerable to attack.
It is discovered that consumption of the spice melange has the effect of both bolstering immunity to the retrovirus and stopping its progression in some of those already infected. Omnius, unaware that the virus has been effectively stopped, prepares for the second phase of his attack. Gathering the bulk of the machine armies stationed at the different synchronized planets, the evermind launches the massive fleet towards the League capital Salusa Secundus.
The Great Purge
After learning of the imminent destruction headed their way in the form of the machine fleet, Vorian Atreides formulates a plan whereby the humans can launch pulse-atomic attacks on all of the undefended Synchronized Worlds, ridding the universe of Omnius altogether. However, this plan called for the use of the still unreliable space-folding technology in order to carry out the attacks before the machines have a chance to recall the fleet en route to Salusa.
The Great Purge is successful in destroying Omnius on all but one planet, albeit with an appalling cost in human lives. Each time the human armies fold space to a new location there is a 10% attrition rate due to the undependable space-folders. In addition, the use of atomics kills all human captives on the Synchronized Worlds, amounting to billions of lives lost. The humans are also unable to destroy Omnius on the primary synchronized world, Corrin. While the other Evermind incarnations are being attacked, the cogitor Vidad travels to Corrin and warns Omnius Prime of the human counter-offensive. The machine fleet is recalled to defend their last remaining stronghold. Despite this, Serena Butler’s Jihad is declared over.
