Beastmaster

From HammerWiki

The Dark Elves have had exceptional people adept at bending beasts and folk to their will. Those that show an usual talent for this and have the ability to command beasts with a single firm word are known as Beastmasters. Those talented with this gift are trained in the city of Karond Kar to perfect their skills.

The Beastmaster also serve as slavehandlers, Humans, Orcs or the other lesser races are the equivalent of beasts, so them being handled like any other beast is only natural.