As Dune begins, Feyd-Rautha figures heavily in the Baron's plans to gain power for House Harkonnen. The Baron favors the handsome and charismatic Feyd over Feyd's older brother Glossu Rabban ("The Beast") because of Feyd's extreme intelligence and his dedication to the Harkonnen culture of carefully-planned and subtly executed sadism and cruelty, as opposed to Rabban's outright brutality.
The Baron could see the path ahead of him. One day, a Harkonnen would be Emperor. Not himself, and no spawn of his loins. But a Harkonnen. Not this Rabban he'd summoned, of course. But Rabban's younger brother, young Feyd-Rautha. There was a sharpness to the boy that the Baron enjoyed ... a ferocity ... A year or two more — say, by the time he's seventeen, I'll know for certain whether he's the tool that House Harkonnen requires to gain the throne.
Feyd is, for a while, the Baron's heir, or na-Baron. To assure Feyd's power, the Baron intends to install him as ruler of Arrakis after a period of tyrannical misrule by Rabban, making Feyd appear to be the savior of the people.
Feyd, like Paul Atreides, is also the product of a centuries-long breeding program organized by the Bene Gesserit, who planned their own alliance by joining a Harkonnen son to an Atreides daughter with the expectation that their offspring would have a high probability of being their hoped-for Kwisatz Haderach. For this reason, Lady Jessica's decision to defy the Sisterhood and to produce an Atreides son, Paul, threw the Bene Gesserit's plans into turmoil and established an irreconcilable tension between Feyd and Paul as the scions of their bitterly opposed noble houses. The risk of one or both of these young men being killed, destroying thousands of years of genetic engineering, is so great that the Bene Gesserit send an envoy, Margot Fenring, to seduce Feyd and conceive a child, salvaging his genetic material.
Margot also intends to "plant deep in his deepest self the necessary prana-bindu phrases to bend him," which she later refers to as the "Hypno-ligation of that Feyd-Rautha's psyche." Presumably he is thus "prepared" and made vulnerable to a command which will cause complete muscle paralysis, a technique the Bene Gesserit sometimes use on individuals who are considered highly dangerous.[4] It is also later noted by the Reverend Mother Mohiam that Feyd's encounter with Lady Fenring produced a daughter.
Feyd's ambition and impatience to inherit the Baron's title and power spur him to attempt his uncle's assassination; as punishment for the failed attempt, the Baron forces Feyd to single-handedly slaughter all the female slaves who serve as his lovers. He explains that Feyd has to learn the price of failure.
As Paul makes his final bid to usurp the Padishah Emperor's power, he is challenged by Feyd. Though famed for his prowess in single combat, Feyd intends to guarantee victory by breaking the formal rules of kanly (which govern this type of challenge) and using a hidden poison spur in his fighting outfit. He nearly succeeds in killing Paul in the ritualized fight, as Paul struggles with whether to try the paralysis word-sound and owe the Bene Gesserit his victory, or to risk his life against Feyd in a "fair" fight. Paul manages to defeat Feyd without the command, and goes on to ascend the throne of the Emperor.