The Bene Gesserit are an exclusive sisterhood whose members train their bodies and minds through years of physical and mental conditioning to obtain superhuman powers and abilities that seem magical to outsiders.

Members who have acquired the breadth of Bene Gesserit abilities are called Reverend Mothers, and play roles of greater importance in the development of the sisterhood's schemes.

Sotericus Rebecca Nesah is a tall, pale-skinned Reverend Mother, whose apparent young age may suggest an unusual talent that granted her the rank earlier than most were.