Reverend Mother Gaius Helen Mohiam was a Bene Gesserit Reverend Mother. Mohiam trained the Lady Jessica in the Bene Gesserit chapterhouse on Wallach IX. Two decades later, Mohiam tested the young Paul Atreides before his departure for Arrakis with the gom jabbar. The test was to discover whether Paul was "truly human" by trial of pain. The pain inflicted on Paul was caused by nerve induction and clearly drained an incredible amount of energy from the Reverend Mother, since no male child had ever withstood that much physical pain before.
Mohiam joined the conspiracy to topple the rule of Paul Atreides after he ascended the Golden Lion Throne and unleashed his Jihad upon the Empire. She, along with Scytale (a Tleilaxu Face Dancer), Edric (a Guild Navigator), and Irulan Corrino (embittered wife of Paul Atreides), plotted to insinuate, as the Emperor's Reverend Mother, the Tleilaxu ghola Hayt into the court to weaken Paul's confidence in his prescience and thereby ruin him. When the plot failed, she was executed in the retaliation initiated by Alia Atreides after Paul walked into the desert after the death of Chani, ignoring Paul's instructions that Mohiam be spared.
Behind the ScenesEdit
The prequel novels by Brian Herbert and Kevin J. Anderson reveal that Mohiam was secretly the mother of Jessica and grandmother of Paul. This occurred as a result of a vicious rape by the Baron Harkonnen, although she had been commanded by the Sisterhood to become pregnant with the Baron's daughter for their breeding program. According of Herbert and Anderson, this twist was discovered in notes left behind by Frank Herbert.
However, Lady Jessica would have known the true identity of her mother through Other Memory when she took the Water of Life. So too, Alia would have known her grandmother's true identity, as would have Paul, Leto II, and Ghanima. None of these individuals mentioned Mohiam in this context, although this may be the reason that Paul left instructions that she be spared.