Who is Reverend Mother Superior Alma Mavis Taraza from Heretics of Dune and what is their importance?

The Reverend Mother Superior of the Bene Gesserit Sisterhood when the novel opens, Taraza is tall, supple and graceful. No longer trusting the Reverend Mother Schwangyu to train and protect the twelfth Duncan Idaho ghola on Gammu, Taraza sends the Reverend Mother Lucilla to imprint the boy sexually. Taraza sees clearly that whatever benefits the Sisterhood is good and whatever opposes it - particularly the "Honored Matres" returning from the Scattering, is bad. Taraza remarks that while conflicts under the Golden Path are a mere 2% of those before, there are forces at work seeking to return to pre-Tyrant conditions.