Agamemnon was the ruthless leader of the cymek Titans, the biological father of Vorian Atreides, and a key figure in history leading up to the Butlerian Jihad.
Upbringing
Born Andrew Skouros on Earth, Agamemnon was the recipient of a pampered upbringing during the end of the Old Empire. As a teenager, Skouros grew unsatisfied with the apparently meaningless direction of society. He became fascinated with ancient legends and myths, and studied the military victories of eons ago. Around this time Skouros took the alias "Agamemnon", after the ancient Greek military ruler.
Rise of the Titans
During countless hours playing online computer strategy games, Agamemnon met Juno, an equally ambitious rebel, who had named herself after the mythical wife of Jupiter. The two began a torrid physical affair which saw them experiment with numerous pleasurable psychological and technological concepts.
After hearing the reactionary Tlaloc speak, Agamemnon and Juno decided to join his solitary crusade. After months of planning they welcomed the technology genius Barbarossa, along with others, into their midst, and called themselves the Titans. Using cunning and technology the group initiated a takeover of the artificial intelligence framework, on which society had become utterly dependent.
After defeating most of the Old Empire (through a chain of largely violence-free victories), the Titans declared themselves the new rulers of the various planets that had made up the Empire. Agamemnon, as their leader, took the title of General, and with the others pursued a strategy of brutal rule over all their human subjects.
During the centuries-long rule of the Titans, Agamemnon first applied biological treatments to prolong his life, and then later discarded his human body altogether by transferring his brain into mechanized physical form, turning himself into a cymek.
The Rise of Omnius
When his fellow Titan Xerxes accidentally ceded too much control to the artificial intelligence network on his planet, Omnius came into being, and Agamemnon found himself no longer a ruler.
During the thousand-or-so years of Omnius' rule, Agamemnon remained a silent but jealous military servant. His time was spent raging against the free humans in the League of Nobles, and commissioning grandiose memorials to the Time of Titans.
Re-emergence of the Titans
Seizing on the escalation in tensions between the League of Nobles and Omnius' Synchronized Worlds, Agamemnon implemented a break away for the remaining Titans, thanks in no small part to the efforts of the neo-cymek Beowulf. The group successfully disabled the Omnius incarnation on the planet Bela Tegeuse, and declared themselves the new rulers of the cowed slave population on the planet.
After indoctrinating the populace, many were willingly converted into neo-cymek, and served as Agamemnon's new army in his conquering of the planets synchronized world Richese and Hessra, the ice world of the cogitors. He later launched a campaign to take control of the Synchronized Worlds that had been sterilized during the Army of the Jihad's Great Purge.
Death
Agamemnon was ultimately killed by his biological son, Vorian Atreides. After Vorian had apparently abandoned the League of Nobles and infiltrated the rebellious Titans, he conspired with the captured Quentin Butler and destroyed the remaining Titans in their Hessra stronghold. Agamemnon was the penultimate Titan to die, being briefly outlived by his compatriot Dante.
Behind the Scenes
In Children of Dune, by Frank Herbert, right before Alia began one of her internal conversations with the ego-memory of Baron Vladimir Harkonnen an ego-memory called "Agamemnon" begged for some attention.
Therefore, Agamemnon seems to exist in the universe created by Frank Herbert, but he could yet be a different character. It is very likely that the ego-memory Agamemnon is meant to be that of the historical Agamemnon of the House of Atreus.
It is possible that Brian Herbert took the idea of this prequel novel character from the notes of his father.