Khan of Khans
The Khan of Khans is a self-proclaimed title, or sometimes a title granted by popular acclaim of a Khan's followers. The title implies that a large number of the Horse Clans recognize the leader as the leader of many of the clans. The Khan of Khans generally does not last very long, as often when the person dies, the assembled clans either fight amongst themselves, or disperse, or some combination of the two.
Source of Authority
This title is self-proclaimed, but only recognized when a multitude of clans recognize it, and it can be taken away just as easily, if the clans abandon the person.