The Awakened Council
The awakened council is a special committee called together only in times of great peril or need. It is made up of every Hierarch in the World, and therefore the number of Mages in the council is not linear.
A meeting is called when five or more Hierarchs deem it necessary and issue The Call, a magical message that reaches every Hierarch in the world. The meeting location is usually chosen by the issuers of The Call, but in the past has mostly been a magical construction not quite in any one space or time, for security.
The Awakened Council is group that created the Ouroboros Cabal and they are the only ones that may call it into being.