Margot is the Bene Gesserit wife of Count Hasimir Fenring, a close friend of the Padishah Emperor Shaddam IV, but is loyal to the Sisterhood.

[3][4] Margot's Bene Gesserit abilities include acute observation and awareness, seduction and sexual imprinting, and precise control of her body chemistry, which allows her to ensure conception and choose the sex of the child.

[3]Margot appears in Herbert's novel Dune (1965), in which she warns fellow Bene Gesserit Lady Jessica of impending danger to the Atreides, and is later sent by the Sisterhood to visit Feyd-Rautha Harkonnen.

In Dune, Duke Leto Atreides accepts stewardship of the lucrative but dangerous desert planet Arrakis, previously controlled by his enemy, Baron Vladimir Harkonnen.

Leto's Bene Gesserit concubine, Lady Jessica, discovers a coded message from Margot, the wife of the former governor of Arrakis, Count Fenring.

[7] During the events of Dune: House Atreides, unmarried Margot Rashino-Zea is hand-selected by Bene Gesserit Kwisatz Mother Anirul to infiltrate the household of Abulurd Harkonnen on Lankiveil.

Margot soon discovers that the Harkonnens have been grossly underreporting melange production to CHOAM and the Padishah Emperor Elrood IX, and are stockpiling it for their own purposes.

Margot and her future husband Count Fenring later convince Emperor Shaddam IV to marry Reverend Mother Anirul by explaining the benefits of an alliance with the Bene Gesserit.

[8] In Dune: House Harkonnen, Margot seeks out the Fremen on Arrakis in search of a group of Bene Gesserit sisters working on the Missionaria Protectiva, including the Reverend Mother Ramallo, who had previously disappeared.

[15] Alia manages to kill Marie, but Margot's revelation of her daughter's paternity surprises Paul enough to allow Count Fenring to stab him mortally.