The Black Ajah is a secret society of Aes Sedai who have forsaken the Three Oaths. This Ajah supports the Dark One, and its members are also active members of the other seven Ajahs to keep their anonymity.
The Black Ajah has been secret until quite recently. Their existence was not acknowledged (in fact it was considered almost dangerous to mention the Black Ajah to Aes Sedai) until Liandrin and a group of twelve other Blacks fled the Tower with a number of stolen items of the One Power. The Black Ajah currently has its own set of oaths, of which only one has been revealed: it prohibits members of the Ajah from revealing other sisters as Black, the existence of the Ajah at all, or the Ajah’s current plans.
It is believed that the Black Ajah was founded by the Forsaken Ishamael, but currently it reports to Mesaana, who is undercover in the White Tower. The Ajah is administered by a supreme council of thirteen, the head of which is Alviarin Freidhen, the only member of the Black Ajah to know the identites of all Black sisters.
The Black Ajah is organized into a series of units called hearts. The hearts consist of three sisters who know only each other and one other woman from another heart.
Notable members of the Black Ajah include: Liandrin, Temaile Kinderode, Rianna Andomeran, Eldrith Jhondar, Joiya Byir, Chesmal Emry, Berylla Naron, Jeaine Caide, Asne Zeramene, Amico Nagoyin, Marillin Gemalphin, Falion Bhoda, Ispan Shefar, Alviarin Freidhen, Galina Casban (formerly second highest-ranking Black sister until her capture by the Shaido Aiel), Talene Minly, Katerine Alruddin, Elza Penfell, Careane Fransi and Delana Mosalaine.