The Titans of the Dune universe were a group of human revolutionaries turned overlords, some of whom feature in the 'Legends of Dune' prequel novels written by Brian Herbert and Kevin J. Anderson.
Origins of the Titans
The Titans' genesis comes from the decadence of the Old Imperium, which over thousands of years had grown corrupt and inert. Proclaiming the need for change, a revolutionary and political philosopher named Tlaloc emerged from the outer edges of the Known Universe.
A few individuals, totaling 20, became avid followers of his reactionary ideologies, and began a plot to overthrow the Old Empire and instill themselves as new rulers. During this time the group adopted the names of legendary individuals from human history.
Thanks to the cunning tactical leadership of their tactical leader General Agamemnon, the technological genius of Barbarosa, and financial backing from Xerces, a former prince, the group succeeded in gaining access of the Imperial networks, and utilized the countless automatons scattered throughout the Known Universe to gain total control.
At some point prior to or during their uprising, the group's spiritual leader Tlaloc died.
After dividing up control of the various planets between them (though still under the ultimate leadership of Agamemnon), the group enacting their own form of brutal rule upon their subjects. Despite being recipients to age-extension treatements, old age was catching up with the Titans, and so fearing their own demise, they each embarked upon surgery that saw their brains removed from their bodies and placed in preservation tanks. Agamemnon was the first to undergo this surgery, and Xerces the last.
While this action was similar to that taken by the Cogitors, the Titans rejected the option of sensory depravation, and instead forged robotic bodies and sensors to act as replacements for their human forms. Thus were born the original Cymeks.
The Rise of the Thinking Machines
During the rule of the Titans (also known as the Time of Titans), the group relied to a lesser or greater extent on the Thinking Machines - the limited artificial intelligences present in the various networks and robots around them. While many of the Titans sought physical pleasure (usually through violence or sex), the Thinking Machines controlled the daily operations of the new empire.
The Titan Xerces, being particularly fond of physical pleasure, afforded too much autonomy to his regional Thinking Machines network, thus allowing the technological being Omnius to come into being. The sentience of Omnius quickly spread to other worlds before further action could be taken by the Titans, and it took control from the Titans.
Due to cautionary programming by the Titan Barbarosa, Omnius was unable to kill the Titans. But under the constant supervision of Omnius and without a powerbase, the group were left as harmless celebrities. They spent their time commissioning grandiose statues and buildings depicting their glory days, and seething at both Omnius (silently) and the hgrethir - the word coined by the Titans for the free humans, particularly the League of Nobles.
Decline of the Titans
During the Butlerian Jihad, the remaining Titans, along with some Neo-Cymeks, seized an opportunity to break free of Omnius and gain control of the planet Bela Tegeuse. After creating an army of rabid and subservient Neo-Cymeks they gained control of at least on other planet Richese, and eagerly sought to establish a new Time of Titans. However, the nebulous empire was conquered and destroyed towards the end of the Butlerian Jihad.