Lady Jessica

Ten thousand years before Jessica is born, the Sisterhood led by Valya Harkonnen is already doing what the Bene Gesserit will still be doing in Paul's time. The sisters serve as Truthsayers in the courts of the Great Houses, use the Voice to bend other people's will and secretly keep a genetic record of the noble families.

That breeding program, started there, will run for millennia, all the way to Jessica's time.

The Bene Gesserit ordered Jessica to give the Duke a daughter. That girl would have a son, the Kwisatz Haderach, the superhuman the breeding program has chased for generations. Jessica disobeys out of love for Leto and has Paul.

She teaches her son the Voice and control of his body. When Reverend Mother Mohiam, her old teacher, comes to Caladan to test Paul with the gom jabbar, Jessica waits outside the room reciting the Litany Against Fear, unable to do anything.

On Arrakis, the Fremen housekeeper Shadout Mapes hands Jessica a crysknife and watches her as if she were a figure out of a prophecy. Jessica understands what's going on: centuries ago the Bene Gesserit planted legends among the Fremen to protect any sister who might one day need them.

On the night of the Harkonnen attack, Jessica and Paul are bound and flown out to die in the desert. Jessica uses the Voice to overpower their captors, who end up dead. After losing Leto and Duncan, she flees with her son through a sandstorm.

In the tent, Paul says what she hadn't told him yet: she is pregnant. When Stilgar's Fremen find them, Jamis challenges the outsiders to a duel, and Jessica watches her son kill Jamis.

At Sietch Tabr, Stilgar orders Jessica to replace the tribe's dying Reverend Mother. To do so she drinks the Water of Life, a poison that kills almost everyone who tastes it. Jessica survives, transforms the poison, receives the memories of the Reverend Mothers before her and awakens the mind of her unborn daughter, Alia, whom she starts talking to.

With her face tattooed in the Fremen way, she uses her new standing to spread the prophecy of the Lisan al Gaib and travels south to convince the fundamentalists that Paul is the messiah.

After drinking the Water of Life, Paul sees what the Bene Gesserit program kept hidden: Jessica is the daughter of Baron Vladimir Harkonnen, the enemy who destroyed House Atreides. Mother and son carry the blood of both rival houses.

In the end, Jessica watches her son take the throne and launch the holy war she herself helped set up. Rebecca Ferguson is confirmed for Dune: Part Three, which opens on December 18, 2026.

In Frank Herbert's novel, it's in the desert tent, still in Book One, that Paul tells Jessica she is the Baron's daughter; she didn't know. Her mother's identity only shows up in the prequel novels by Brian Herbert and Kevin J. Anderson: Reverend Mother Mohiam herself. In the novel, Alia is born during the story and is an unsettling child who talks like an adult. Jessica is also less calculating than in Villeneuve's movies and, at the end, comforts Chani by saying history will call them wives.