Bene Gesserit
In "Dune", Padishah Emperor of the known universe Shaddam IV keeps the wise but calculating Bene Gesserit Truthsayer Mohiam by his side at all times. The Emperor's deceased wife, Anirul, had been a "Bene Gesserit of Hidden Rank", and Herbert notes that every one of their five daughters is Bene Gesserit-trained. In fact, Shaddam is kept without a male heir on specific orders from the Sisterhood, and is bound by an agreement that only a daughter will ascend his throne. The Bene Gesserit had also placed their acolyte Jessica (herself the product of a secret Bene Gesserit liaison with the Baron Harkonnen) as the concubine to Duke Leto Atreides, and married the Bene Gesserit Margot to Shaddam's close friend and minion Count Fenring. After Shaddam's eldest daughter Princess Irulan is forced into marriage to Paul to secure his claim to the Imperial throne, in "Children of Dune" Irulan's loyalty to the Sisterhood gives them false hope that she can help them topple Paul, or at least control his offspring. Later in "God Emperor of Dune", Herbert establishes that despite Leto's many restrictions on them, the Bene Gesserit still train young noblewomen for a price. In fact, when Leto meets Hwi Noree, the Ixian ambassador obviously bred and trained to charm him, he realizes "that part of her education had been conducted by the Bene Gesserit. She had their way of controlling her responses, of sensing the undertones in a conversation. He could see, however, that the Bene Gesserit overlay had been a delicate thing, never penetrating the basic sweetness of her nature."