The Lady Helena Atreides (nee Richese), was the wife of Duke Paulus Atreides, the mother of Duke Leto Atreides I, and the grandmother of Padishah Emperor Paul Atreides.
History
Paulus & Leto
Her marriage to Paulus was political in nature, and the couple had little in common and limited love for one another. Partly as a result of this and partly because of Helena's continued allegiance to House Richese, they gradually drifted apart until they were on acrimonious terms. She did, however, maintain a perfect front during important meetings and public events and fussed about her own appearance. During her spare time, she preferred to study the Orange Catholic Bible and other religious texts.
She was not warm to Leto, and often said she would never have any more children. She bore a son only out of duty to House Atreides, rather than out of a natural maternal instinct. When Leto was about to leave for Ix, she insisted to Paulus to send him somewhere else.
Exiles from Ix
Paulus' and Helena's relationship reached a new low while their only son was living on Ix. When Leto returned to Caladan, with the exiled children of House Vernius, Rhombur Vernius and Kailea Vernius, Helena was strongly against their taking refuge in Castle Caladan with House Atreides. She believed that House Vernius had been exiled from Ix because of their affront to God, and that they were being punished by coming close to building Thinking Machines.
Assassinating Paulus
After a year, Helena began to secretly plot against Paulus, as she strongly believed that he was doing irrovcable harm to his ducal position. Helena secretly arranged for the salusan bull Paulus was to fight to be drugged, and the bull ended up killing Duke Paulus. Upon discovering her involvement in his father's death, Leto exiled her to Caladan's sparsely populated Eastern Continent, where she became a religious student of the Sisters in Isolation.
Pleading to Help House Richese
A few years later, when the Emperor Shaddam Corrino IV attacked Korona, an artifical moon of Richese, during the Great Spice War; the resulting damage to the planet below was catastrophic. Helena found out about the plight of her maiden people and trekked across Caladan, to ask Leto to help the plight of her former planet. Out of compassion for his mother's House and planet of her youth, Leto agreed to send relief aid.
Meeting Paul and Death
Over ten years later, during the War of Assassins of 10,187 AG, Duncan Idaho and Paul Atreides, whom Idaho had sworn to protect, fled their attempted murderers by taking flight to the sparsely populated Eastern Continent on Caladan. After a trek through the dense jungle, Idaho decided to take refuge with the Sisters in their Abbey. Paul met his grandmother, Lady Helena -- who had risen to Abbess of the organization -- for the first time; although Helena was not especially warm to her grandchild.
Helena castigated Idaho for bringing young Atreides to the Sisters, speaking of their desire to remain in peace and obscurity. Although the Grumman mercenaries had been unable to find the two for almost a week, once they realized where the duo were, they mercilessly attacked the abbey. Instead of deciding to flee or put up resistance, Helena chose to continue to her meditative weaving, as the giant building came crashing down around her, and she was killed by falling rubble.