The Great Purge was en event in modern Aes Sedai history, taking place in 1000 NE.[1][2]
Egwene al'Vere, after learning the Black Ajah's member lists from Verin Mathwin's secret notes[3], returned to the rebel camp. After assembling the Rebel Hall of the Tower and swearing the three oaths on the Oath Rod and thereby proving herself not a Darkfriend, she claimed to know the names of the Black Ajah's members, several of them found among the rebels. Among the Hall's present members, Moria Karentanis, a Sitter of the Blue Ajah was discovered as Black, shielded and blocked, the same happening to Egwene's Keeper of the Chronicles, Sheriam Bayanar. The Hall then proceeded by forsaking and reswearing their oaths on the Oath Rod in turn, in order to prove themselves friends of the Light. Afterwards, they had all the Rebel Aes Sedai come by Ajah to repeat the process, resulting in over fifty Black sisters captured out of the estimated seventy that were in camp at the time.
Afterwards, back in the White Tower and in control of both factions as the true Amyrlin Seat, Egwene repeated the process within the Tower. But before the Purge started the majority of Black sisters inside the Tower, around sixty, was alerted and they were able to flee; so only a dozen of them was captured and executed.
Somehow Mesaana was able to escape the reswearing process and she was not found. About it Seaine, Yukiri and Doesine theorized some methods to evade the power of the Oath Rod. But Egwene was aware of the Mesaana's presence in the Tower, due to Verin's warnings in the notebook, Sheriam's confession, and Egwene's own feelings, so the young Amyrlin vowed to hunt her down if she had dared to remain in the Tower.[4]