HBO's Dune: Prophecy has a wide and varied cast, but it is primarily the story of Valya and Tula Harkonnen, two sisters from a disgraced House who rise to become powerful figures within the Bene Gesserit Sisterhood. The Dune: Prophecy creative team chose to tell Valya and Tula's stories both in their present day, with the characters played by Emily Watson and Olivia Williams, and in flashbacks to their childhoods, with the sisters portrayed by Jessica Barden and Emma Canning, respectively. This was an effective storytelling choice that allowed the audience to see just how much Valya and Tula had grown and changed, as well as the events that ultimately shaped who they became as adults.