A Reverend Mother was a title held by female members of the Bene Gesserit who had completed training to an advanced level. Typically, Reverend Mothers had three names: The first was a Latin male name, the second an English female name, the third an Arabic or exotic name. Examples of such naming include Gaius Helen Mohiam, and Alma Mavis Taraza. The leader of the Bene Gesserit, the Reverend Mother Superior, was always chosen from the Reverend Mother ranks.
After completing many years of intellectual, physical, and psychological training with the Bene Gesserit Sisterhood, a prospective Reverend Mother underwent a dangerous ritual that involved a significant amount of awareness spectrum narcotics. Specifically, the poison used was the Water of Life - the liquid exhalation of a sandworm produced at the moment of its death by drowning in regular water.
The drug entered her body as a poison, and it was her task to consciously transform the chemical into a benign substance in a process known as the spice agony. If the subject survived the process, the physical and mental trauma caused by the spice agony would cause their Other Memory to emerge, that is, she would gain the memories of all her female ancestors, resulting in a sudden and immense accumulation of knowledge and power.
The Water of Life will turn the eyes of a Reverend Mother completely blue, even if she was not addicted to melange prior to her spice agony.
Mentat Bene Gesserit
All Bene Gesserit Mentats (like Tertius Eileen Anteac and Bellonda) were pre-conditioned Reverend Mothers, who, in addition to the standard abilities of a Bene Gesserit, and the unlocked Other Memory of a Reverend Mother, also possessed the skills of supralogical strategizing, tacticizing, and hypothesizing of a Mentat (skills which surpassed even those of the pre-Butlerian Jihad Thinking Machines).
Male Bene Gesserit
Until the rise of Paul Atreides, the Water of Life ritual had been fatal to every male who had attempted it. In an extensive breeding program, the Bene Gesserit produced a single male who survived the transformation, a male version of a Bene Gesserit Reverend Mother (a 'Reverend Father' of sorts), the so-called Kwisatz Haderach (who posses the male and female genetic memories as well as total prescience). By the original plan of the Bene Gesserit, the Kwisatz Haderach would have been born from the union of a son of House Harkonnen and a daughter of House Atreides. Paul Atreides was the final, albeit unexpected, result of this strategy.
Miles Teg was also a product of the Bene Gesserit breeding program, down the line of the House Atreides genes, and (though his mother, Reverend Mother Janet Roxbrough) received much of the Bene Gesserit learning instilled in Reverend Mothers, as part of his training to eventually become the Supreme Bashar of the Sisterhood. Therefore, while not a Kwisatz Haderach, Miles, like Paul Atreides, was both a Mentat and a Bene Gesserit adept.
Reverend Mother Gaius Helen Mohiam to Lady Jessica Atreides
- "You thought only of a Duke's desire for a son?
- ... Desires don't figure in this! An Atreides daughter
- could have been wed to a Harkonnen heir and sealed the breach.
- We may lose both blood lines now."
Wild Reverend Mothers
Unbeknown to many in the Imperium, some fringe cultures produced wild Reverend Mothers who possessed many of the skills of a Bene Gesserit Reverend Mother, but without the official training. It should be noted that even these "wild" Reverend Mothers ultimately owed their status to the Bene Gesserit anyway, with most of them owing their positions to the religious engineering orchestrated by the Missionaria Protectiva.
Such groups included the Fremen, who had their own independent tradition that emerged from the Missionaria. Such individuals were called Sayyadina. These Sayyadina went through the spice agony and had access to their ancestral female memories; however, they lacked the other skills (such as the Weirding Way) that the Bene Gesserit had developed.
Other Wild Reverend Mothers
Another similar group was a sect of conservative Jews, located on Gammu. Though they still retained their ancestral religious traditions, they also learned many Bene Gesserit secrets, and started to produce their own Reverend Mothers (such as the Jewish Reverend Mother Rebecca). These Jewish Reverend Mothers did not emerge until the time of the Honored Matres, however.
Limitations of Sex
Typically, when women survived the Water of Life and unlocked Other Memory, only the female line of ancestors were visible to them. It was believed that the male side terrified them, for reasons unknown. The Bene Gesserit breeding program was aimed specifically at breeding the Kwisatz Haderach - a male version of a Reverend Mother, who could potentially unlock the memories of both the female and the male ancestral lines.
As explained by Paul Atreides, the first Kwisatz Haderach, every human has within themselves "an ancient force that takes and an ancient force that gives" - a female (such as a Bene Gesserit) is able to fairly easily face her internal "giving force", but is utterly unable to see into her internal "taking force" without changing into something other than a woman, while the exact opposite is true for a male, who, while remaining a man, can fairly easily see into his internal "taking force", yet is unable to peer into his internal "giving force". Hence, Paul claims that he, as the Kwisatz Haderach, is something other than just a male, which allows him to see into both of his ancient internal forces as "the fulcrum", who "cannot give without taking, and cannot take without giving."
There were, however, exceptions to this rule - Alia Atreides and her niece Ghanima Atreides were both capable of seeing the male and female ancestral lines. It should be noted, however, that both women were close relatives of the first Kwisatz Haderach, Paul Atreides - Alia was his sister (who also suffered Abomination, getting possessed by her inner Ego-memories), while Ghanima was his daughter.
The possession of a multitude of ancestral Ego-memories was both a blessing and a curse for those who possessed them - while they provided the individual with immense knowledge from past experiences, the Ego-memories of the person's ancestors could sometimes assert themselves, and eventually govern the person's behavior. At times, this would happen to such an extent that the individual was considered possessed. The term the Bene Gesserit used for this condition was Abomination. The only known cures for Abomination were a Trial of Possession, or death. Avoiding Abomination was actually as simple as waiting until adulthood to undergo the spice agony - once a Sister's personality and individualism were fully developed and matured, there was little danger of possession.
Paul Atreides' sister, Alia Atreides, was accidentally transformed into a Reverend Mother Pre-born: while still in her mother Jessica's womb. The shock and trauma this brought on to the unborn child was catastrophic, and when she was in her early twenties, Alia ultimately succumbed to Abomination, and became possessed by the Ego-memory of her maternal grandfather, the Baron Harkonnen.
Paul's twin children, Leto Atreides II and Ghanima Atreides, were also pre-born like Alia, however, they strove to escape possession. When Leto was apparently killed, Ghanima constructed a mental wall of grief, which induced her conscious self to believe that Leto was indeed dead. This process also cut off her Ego-memories to a level that prohibited possession. Leto, however was forced to consume great quantities of spice, and while claiming he was not possessed, much later admitting this to be a lie, by the definition of the Bene Gesserit. In order to control his inner Ego-memories, Leto turned to one Ego-memory in particular, that of the ancient king Harum. However, this appears to be more of a ruling personality within the personalities Leto contained, rather than one personality taking over his flesh.