In “Dune” lore, Valya and Tula are sisters who become part of an underground organization, the Sisterhood of Rossak, the precursor to the Bene Gesserit from the original novels and Villeneuve’s adaptation. Diane Ademu-John, known for her work on “The Haunting of Bly Manor” and “Medium,” will lead the project as the showrunner, with Villeneuve serving as executive producer.