Thora was a Bene Gesserit Reverend Mother and member of the council of Mother Superior Harishka, in the events of the Prelude to Dune series.
Reverend Mother Thora was in charge of the Sisterhood's orchards, and was an expert in cryptography. She had developed at the beginning of her career a technique consisting on introduce messages on plants. She replaced Reverend Mother Lobia in charge of the orchards, when the old Lobia was required in Kaitain as the Imperial Truthsayer of Emperor Shaddam Corrino IV. Thora participated in Harishka's council to determine if the no-ship should be given or not to Duke Leto Atreides from Caladan, where she affirmed that the Duke was abusing the information given to him years ago. During the session, Harishka realized that Thora was consuming several quantities of Spice coffee.
At the end of Dune: House Corrino, Harishka tought necessary to consult with Thora about certain passages of the deceased Lady Anirul's diary, which was the only surviving memory of the last Kwisatz Mother of the Bene Gesserit.