Rebel Aes Sedai Spies
In an attempt to undermine Elaida’s power, the rebel Aes Sedai send ten sisters back to the White Tower to spread the rumors about Logain being set up by the Red Ajah. They send two sisters from every Ajah except the Blue and the Red (ACoS, Ch. 8; TPoD, Ch. 26). The sisters include Bernaile Gelbarn and Zerah Dacan from the White Ajah (TPoD, Ch. 26), Annharid and Celestin from the Yellow Ajah (CoT, Prologue) and Jennet and Meidani from the Gray Ajah (KoD, Ch. 24).
The "ferrets" are discovered when Seaine and Pevara begin their hunt for the Black Ajah. When Zerah Dacan returned to the White Tower, she told people that she came from the north, yet Seaine and Pevara find Goldenthorn seeds and a red cockle-burr on her saddlecloth, which can only be found south of Tar Valon. Thinking that this lie must mean that Zerah is a member of the Black Ajah, they take her down to the basements, make her re-swear the Three Oaths as well as a fourth oath to obey them, and then make her answer their questions. They thus find out that Zerah actually came from Salidar; she must have ridden around to approach Tar Valon from the north. They also learn that she is a rebel who was sent to spread the rumors about Logain and the Red Ajah, and force her into giving up the names of the other ferrets. Seaine and Pevara decide to use the ferrets to their advantage in hunting the Black Ajah, deciding that they will make all of the other ferrets swear the same fourth oath that they made Zerah swear (TPoD, Ch. 26).
Seaine arranges to have Zerah bring Bernaile Gelbarn, the other White ferret, to her and Pevara to question (TPoD, Ch. 26). They eventually question all of them and bind them with the fourth oath (WH, Prologue). The Black Ajah hunters set the ferrets to work finding out information. Annharid and Celestin are told to find out who Atuan Larisett’s friends are within the Yellow Ajah, and Meidani has also been watching Atuan, as we see her reporting to Yukiri on her. Likely all of the ferrets have been keeping an eye on her. Yukiri also orders Meidani to renew an old friendship with Elaida, so that they can keep an eye on her (CoT, Prologue).
When Beonin, who has been spying on the Salidar Aes Sedai, returns to the White Tower, she tells Elaida all about the ferrets. Tarna wants to know if she should have them arrested, but Elaida tells her to simply have them watched, to see who they associate with. She also tells Tarna to have Meidani invited to dinner with her, since she now knows why Meidani has been trying to renew their friendship (KoD, Ch. 2).
Although Beonin has betrayed the ferrets to Elaida, she warns Meidani and Jennet, the two Gray ferrets, of what she has done. When Egwene learns that Beonin is in the Tower, she orders her to warn the other ferrets as well (KoD, Ch. 24).
When Tarna later sees Elaida and Meidani dining together, Elaida seems very predatory and Meidani looks nervous. Although Elaida has learned nothing from Meidani so far, she thinks that he rebel is trying to renew their old relationship as pillow-friends, and Elaida is considering letting her do so in the hopes that Meidani will reveal more that way (KoD, Ch. 25). Elaida also orders that the Sitters have the ferrets watched, although she will not allow the Sitters to be told why. She thinks that some of the Sitters might be working with them (KoD, Ch. 25).
Elaida contines to pretend friendship with Meidani, taking pleasure from mocking and intimidating her (TGS, Ch. 2). When Egwene finds out, she tells Meidani her work is appreciated and tells the Black Ajah Hunters that they should release the spies from the fourth oath (TGS, Ch. 16). They are reluctant at first, but eventually agree (TGS, Ch. 40).