Alliance between two or more of arialian tribes that were widely spread in the 500AC - 1250AC on the Arial early represented simple trusts between tribes but further led them into trading and helping each other against common enemies.
Hierarchy
Officially all the tribes are equal in the rights and do not have rights to intervent into inner business of each other. That has not stopped formation of more important tribes taking charge in decision making.
Council of Elders
The Council of Elders was an early government organ that consisted of the most respectable members of the master clans from each tribe. All decisions were made through voting where the majority would resolve if the idea should be accepted, whether it is some trading agreement or starting war one someone.