From Dune Wiki: Mother Superior Valya Harkonnen [b. 26 BG] was a member of House Harkonnen from Lankiveil who became the second Reverend Mother Superior of the Bene Gesserit Order, its first Mother Superior under that name, after transforming into one of the first Reverend Mothers in history. She first appeared in the 2012 novel Sisterhood of Dune.