Leonin

If you were to ask a Beastlander which race is the most important, they would almost invariably answer with their own and have many reasons why their answer is the correct one. In contrast, if you asked a Leonin, they would have one simple reason: "Without us, there would be no Beastlands."
While this attitude is undoubtedly an exaggeration, the fact remains that Beastlander armies are so formidable in large part due to the heavy presence of Leonin warriors. Raised in their nomadic tribes travelling across the unforgiving grasslands of the Ghasrian Plains, leonin take very easily to military discipline. In the Empire's legion there is a saying: "If you see a leonin's back, that means they're dead." Leonin warbands do not falter and do not break. Even retreats are orderly, disciplined affairs and leonin would rather die than be routed.
When not fighting a war or border skirmish, life in a leonin tribe, while not easy, could accurately be described as peaceful or even boring. Leonin hierarchies are loose, their governance egalitarian, and they are disinclined to fight amoungst themselves.