The Indigo Ajah of the Grey Tower is devoted to the study of Talents and objects of the One Power. It was one of the seven founding Ajahs of the Grey Tower, replacing the Red Ajah from the White Tower, whose guiding philosophy did not fit the purpose of a Tower full of male channellers.
Indigos have been known to study everything from the expression of Talents, to rediscovering lost Talents, as well as finding new ones. The members of the Ajah also study and often create objects of the Power. The Indigo Ajah is responsible for maintaining the Grey Tower's Vaults, and studying various angreal and sa'angreal. Most Aes Sedai and Asha'man who study objects of the One Power are members of the Ajah.
Indigos that have gone on to have major roles in the Grey Tower's leadership include:
- Xeia Loragan, the 2nd Amyrlin Seat
- Elia Darrow, the 17th Amyrlin Seat and the 22nd Mistress of Novices
- Melabrid Daleb, the 4th M'Hael and 3rd Keeper of the Chronicles
- Daimenin al'Donai, the 10th M'Hael and the 11th Master of Soldiers
- Aric Cosamaru, the 12th M'Hael and the 2nd Warder-Channeller Representative
- Corenne Marville, the 6th Keeper of the Chronicles
- Illyria Malkom, the 16th Keeper of the Chronicles and the 18th Mistress of Novices
- Lembirt Antii, the 3rd Keeper of the Archives and the 12th and 14th Master of Soldiers
- Jerid Walker, the 5th Keeper of the Archives and the 15th Master of Soldiers
- Zaephra Wyrd, the 14th Mistress of Novices
- Jhanic, the 22nd Master of Soldiers