“Dune: Prophecy” mainly focuses on the Sisterhood, a group of women who eventually become the Bene Gesserit (who, by the time of the main “Dune” storyline, use their mind-controlling powers and talent for shaping the religious beliefs of far-flung societies to control galactic politics).

The ancient conflict, known as the Butlerian Jihad in Frank Herbert's books, will be glimpsed in HBO's new prequel series.

A long-gestating prequel, about the women who seek to guide a galaxy, is splashy, somber and insufficiently spicy.