Aethorsae

This Centaur  tribe in the western steppe claims to have migrated from farther eastwards, where they were once betrayed by the Geryatae tribe who seized their lands and drove them off. Rauhshna, the Aethorsae queen stared at the starry sky for three nights, choosing between vengeance or migration. In the end she took her tribe west, while urging her people to accept and to forgive. Three generations later, when the Geryata themselves were driven west, the two tribes became friends, then allies, then confederates.
After their westward migration the tribe is close to human settlements, although their lands extend deeper into the steppe, which makes them a vital link in trade that connects the human Skyria to the deep steppe. The Aethorsae are involved in human politics, and involve the nearby human groups in their steppe politics as well. The rise of the Emdarian empire and the relative peace means that any alliances formed, are against the Orcs or other tribes of the steppe.
The Aethorsae are a middling tribe, on the smaller side, of perhaps 40 groups roaming their tribal lands. They gather each year at the Kurgan of Rauhshna to maintain their ties to one another, remember their westward migration and the queen’s wisdom in eschewing bloody vengeance. The gathering at the kurgan also serves as a market, with the clans and even outsiders coming there to exchange goods. The elders meet there to reach decisions that affect the whole of the Aethorsae, and to appoint, depose or confirm a ruler. The Geryatae and the human house Reindal are always welcome as the guests of honour at the ceremony.
Mercenary service in Emdar is seen as an honorable profession, and as truly great game is absent that far west, many would-be heroes choose this path to make a name for themselves. While trade is important, the Aethorsae typically serve as just another link in the chain, but they are a vital link due to the relationships they carefully cultivate with the other tribes and with human Skyria.
The royal position is de-facto life-long and hereditary, as it is seen as vital to maintaining stronger ties to the humans. Even so, the Aethorsae royalty would barely match the power and wealth of a minor Emdarian house.