Omnius, also known as the Evermind, was a collection of powerful artificially intelligent entities, which existed prior to and during the Butlerian Jihad, and after in the refounded Synchronized Worlds outside the Old Empire.
Though Omnius instances existed on many worlds, each one evolving subtle differences, all instances were bound by a synchronizing process that saw them share the collective experiences of their counterparts. Thus they were frequently referred to as a single being.
Omnius is often cited as the cause of the mankind's long-standing revulsion of technology, particularly computers. Though technically a gender-less being, speech refers to Omnius as a male.
During the Time of the Butlerian Jihad
Omnius came into existence during the Time of Titans, from the AI gel circuitry network programmed by Titan Barbarossa. The Titan Xerxes being too docile himself to administer one of his planets, ceded too much control to the thinking machines, resulting therefore the emergence of a self-aware program.
Barbarossa had made the AIs to have ambition and expansion tendencies, in order to facilitate the Titans' rebellion. Omnius therefore (as the intelligence christened itself), quickly took control of the Titan-ruled worlds and brought his own clinical and logical rule to them. Barbarossa however had secured some algorithms that prevented these programs/Omnius to harm the Titans themselves; although Omnius took control of the Titans, it didn't show any will to get rid of them.
Different Evermind and Incarnations
The vast size of the Omnius-controlled empire proved to be problematic when disseminating and synchronizing information. Thus the Evermind deployed planet-wide clones of himself across his empire, each of which acted technically as equals. However, in practise one incarnation took the initiative with empire wide decisions. This incarnation, known as Omnius Prime, was first located on Earth.
Knowledge was distributed between the various Omnius incarnations via Update Ships, which delivered gel circuitry copies of an Evermind from one planet to another via faster-than-light travel. This cumbersome method was accepted by Omnius because no better solution was discovered or made available. The discovery of instantanious Space travel, via the Spacefolder, by the League of Nobles was a jealously guarded (and successfully kept) secret.
Erasmus had put a sort of experimental bet with Omnius Prime concerning the predictability of humans: Erasmus proposed Omnius to randomly select some loyal trustees, and himself would demonstrate that he could turn them against the thinking machines; this would prove whether reliable humans could be trusted. Omnius however warned Erasmus that if the humans indeed proved unworthy, he would vehemently order their extinction, to Erasmus' dismay, since he would have no experiments.
The wage however turned against Omnius and a rebellion on Earth started, which started the Butlerian Jihad. Omnius' retaliation was the extermination of all human slave population on Earth and sent the Dream Voyager with an update copy of himself to warn the Synchronized Worlds about the event and proceed with the extinction order. However Earth-Omnius himself was destroyed during the assault of the League Worlds, and the update copy of Omnius was captured by Vorian Atreides. After that event, the Omnius of Corrin became the Omnius-Prime, who was ignorant of the details of the abortive wager. The only robotic living witness of the details of was Erasmus, who however kept it to himself.
By the end of the Butlerian Jihad, and specifically after Omnius had unleashed the Omnius Scourge virus upon the League of Nobles, his empire had been reduced to a single planet - Corrin. The virus' catastrophic effect on the free humans drew a fierce counter-strike campaign of nuclear obliteration against the Synchronized Worlds. This event, known more commonly as the Great Purge, ultimately left Omnius pinned down on Corrin for many years.
The last incarnation of Omnius was finally defeated by the armies of free humanity at the Battle of Corrin.
Unbeknownst to the free humans, their victory was not entirely complete. Years before, before the start of the Jihad, an Omnius incarnation on Giedi Prime had attempted to expand into uncharted space as a means of preserving its legacy. To that end the Giedi Prime Omnius distributed large quantities of probes carrying Omnius gelspheres. The probes contained sufficient automization and a self-powered gelsphere, and upon arriving on other worlds were able to synthesize and produce new robotic servants and a new incarnation of the robotic empire. The actions of this Omnius incarnation were never learned by the other Omnius instances, and not fully realized by humanity.
Additionally, in the final Corrin battle the Omnius transmitted radio signals into deep-space containing the whole of his psyche. The scheme was a last, desperate grasp at life by the final Omnius instance. It was unlikely to succeed because the signals were unlikely to reach anything capable of intercepting them before they had dissipated beyond use. Unfortunately for the humans, this transmission reached the hidden robotic empire, and their long-time enemy was effectively reborn, but had no contact with human-kind for over 14,000 years.
Reborn Leader of the Machines
The Honored Matres
Millenium later, after The Scattering promoted by Leto II, the Honored Matres, led by a sub-commander named Lenise, bounded into the re-born Thinking Machine Empire outpost in deep space, and stole the Omnius-controlled Obliterators stored there. This allowed Omnius to an understanding as to where his ancient enemy, humans, existed, and most importantly, the Evermind knew where they had originated from.
Immediately, Omnius launched a large-scale invasion of Matre' controlled Scattering space, and sent a new variant of the Omnius Scourge onto their worlds, such as Rikka's Planet. This caused the Matres' to flee from Omnius, where they crashed into the Old Imperium with the Obliterators in tow, and the Matres' destroyed Imperium worlds as they careened forward fleeing from the Great Enemy -- Omnius.
The Tachyon Net & Enhanced Face Dancers
The forces of discovery for the Thinking Machine ruler, and his secondary, the re-born Erasmus; continued on during their hiatus from human contact. During this time, the robotic empire created the immensely powerful tachyon net. The net originated from the robotic homeworld of Synchrony, and could be invisibly "cast" throughout the cosmos to ensnare vessels or beings located as far as other galaxies. The net could also be used to inflict immense pain or suffering upon beings that Omnius or Erasmus had direct control over.
During the hiatus from humanity, Omnius and Erasmus captured the Enhanced Face Dancers launched by Hidar Fen Ajidica during the time of the late Corrino Empire. Omnius, and especially Erasmus, altered the genetic makeup of the Dancers; so they were impervious to detection, and they installed a kill switch in their genetic make up, that when activated caused them to instantly die.
Obsession with the Kwisatz
Omnius used the Enhanced Face Dancers to infiltrate all aspects of the the Old Empire to promote their agenda. With their leader, Khrone, Omnius secretly attempted to create his own Kwisatz Haderach, or super-being. Khrone used the cells of Paul Atreides left on an attempted assassination blade from the time of the Jihad, and created a clone of the former Atreides Emperor, which they named Paolo. Omnius and Erasmus commanded Khrone to have Paolo's personality altered by having the clone raised by a ghola of Vladimir Harkonnen.
Concurrently, Omnius had been hand-fed information by Erasmus that the Kralizec-prophesied Kwisatz Haderach could be aboard the escaped No-ship Ithaca. Hedging his end-of-the-age bet, Omnius wished to increase his chances of success by both capturing the ship, and by creating the super being by cloning.
As these events unfolded, Omnius launched his vast armada of thinking machines to attack and wipe out all of humanity in a star system by star system genocidal invasion. Omnius also used the newer, more deadly version of the Omnius Scourge to weaken planetary systems before being attacked by his machine starship invaders. As the invasion progressed, his fleet reached the last real bastion of human resistance -- the New Sisterhood's rag tag fleet gathered over Chapterhouse, led by Murbella. Victory seemed assured as the Evermind had secretly pre-plotted that the human fleet be sabotaged by Khrone's Face Dancers, as they had installed faulty mechanical systems in the human starship Obliterator weapons.
On the Day of Kralizec
Concurrently, the Ithaca was captured by the machines, and brought to the capital of Machine Empire at Synchrony. Omnius had Paolo and another ghola of Paul Atreides, duel to the death, as he believed one of them to be the prophesied Ultimate Kwisatz Haderach. Paolo, the apparent victor, then ingested too much of the melange ultraspice and fell into an irreversible coma of ultimate universe expanding prescience. Paul self-healed, and proclaimed to all present that the ultimate super-being was Duncan Idaho.
Omnius gloated as he believed that his time of ultimate victory over humanity had come. The Evermind's Enhanced Face Dancers held key positions of power in the human empire, readied to perform his bidding. His fleet stood ready to destroy the last remnants of human space resistance, as he had human-kind hopelessly outnumbered over Chapterhouse.
However, his age old nemesis, Norma Cenva, now ascended to the level of the Oracle of Infinity or Oracle of Time, re-appeared in the Cathedral. She then banished Omnius to another universe, and followed him in as a guardian to ensure he did not leave, and ended the threat of the Evermind forever. Erasmus continued the traditions of the Evermind for a few hours longer, but eventually decided to merge his codes of the Machine Empire with Idaho's nervous system, and then died. Erasmus continued on in Idaho's Other Memory, as an adviser as man and machine worked together for a bright future.
After his first defeat, the oppression of humans by artificial intelligences remained a powerful concept for thousands of years. The physical and psychological damage caused by Omnius succeeded in scarring the human psyche far deeper than any other historical event.
Though Omnius theoretically possessed no feelings and thus no tangible personality, accounts exist that dispute this. In particular, subtle differences in the reactions of the Omnius incarnations on Earth and Corrin were noted; with the Earth-Omnius exhibiting tolerance toward the experiments and theories of the robot Erasmus, whereas the Corrin-Omnius showed a distinct lack of patience with the rogue robot. Additionally, the Corrin-Omnius often displayed erratic, even paranoid, behaviour. This tendency was exacerbated after he incorporated a copy of Erasmus into his psyche.
In his second incarnation, Omnius is much less tolerant and patient, deciding that human-kind cannot even be governed successfully, and must be eliminated. Even Erasmus cannot tolerate the last incarnation of the Evermind, and feeds him inaccurate information about the Kwisatz Haderach, causing him to be over-concerned about the gholas of Paul Atreides, when it turns out that the ultimate Kwisatz Haderach is a ghola of Duncan Idaho.
Behind the Scenes
Omnius features heavily in the Legends of Dune trilogy written by Brian Herbert and Kevin J. Anderson, as well as their afore-mentioned Sequels of Dune. The various Omnius incarnations constitute the Synchronized Worlds, which jockey with the League of Nobles for control of the Known Universe. Omnius is not mentioned in the original Dune novels by Frank Herbert.
The name Omnius is obviously derived form the Latin root omni-, referring to his simulated omnipresence and omniscience. Like the word 'evermind', it refers to his nature of having copies of himself in all of his subjects.