Animals have been used and are still used in combat pretty much since the beginning. There's a lot of creatures out there that are fierce and would love to just rip whatever they're pointed at to shreds. But to make sure they rip apart the right thing, you need trainers. That's where the Dark Elf Beastmaster comes in. She makes sure those savage monsters only tear up the right troops. You can pick up yours now from Avatars of War.
From the website:
Beastmasters are chosen at an early age, and only those with an innate animal empathy, manage to complete their training without becoming food for their own beasts.
These chosen few are capable of subduing the will of the fiercest monsters, which will obey their orders with devotion.