I'll do my best to help you with ideas, but I really can't play the antagonist for you. I'm already playing two horde leaders and their followers! ;D
For every character I'd suggest coming up with some short and long term goals. What do they each want to achieve, and how are they going to get there? Why does Crow want to be trained by this priest? What will that do for him? Why does the priest need Crow? What is he manipulating his disciples for?
I think it helps if you ignore specifying a characters as good or villainous. Nobody really does stuff just 'for teh evulz', unless they're actually insane or there's something really disturbing them emotionally.
Take Claudia, the leader of my horde. She's killed her sister, abandoned her father and taken her supporters into invading Mossflower with plans to enslave whoever she can, build up her army and re-conquer the Northlands. Murder, levying war, slavery, authoritarian rule of beasts considered lesser than she. All very evil sounding on the face of it, but I did not create her with 'being evil' in mind, nor do I write her as a 'bad beast' as someone commented on the chatbox the other day. I write her as a person with fears and hopes, things that make her happy and things she disapproves of. The things she does that are 'evil' are not seen as evil by her, obviously. She thinks herself justified in killing her sister because her sister betrayed her. She thinks slavery is acceptable because she grew up with vermin being subservient to cats as the norm. She wouldn't understand if you told her all beasts were equal, because it does not match her worldview, it does not match her background or the culture of her homeland.
Another example would be Fiasco, my feral cat who is the Taggerung of a Juska tribe. On the face of it, he is brutish, prone to violence, arrogant and superior as well as incredibly moody. At a glance, he would just be another 'bad beast' with no redeeming features. There's a lot more going on with him under the surface though. He's big, but actually barely out of his teens. He's mentally immature, and hasn't socialised much with beasts of his age. His closest friend is a veteran warrior ferret who's a generation older than him. He has emotional issues because he seeks the attention, approval and affection of his adoptive father. His surrogate mother is dead, and that has also left his mark on him, since his original birth parents are also absent from his life. To complicate matters further, he's been made Taggerung, a massive responsibility for someone so young and lacking in a lot of warrior experience. I don't write him as just a thug that can smash things. He's just a big kid with some social troubles, and his 'family' of Juska tribesbeasts have to be very patient to keep him out of too much trouble and let him grow and develop.
So when you write your antagonist, give him some good reasons for why he behaves like he does. If he is cunning, why is he so? Was there a time when he was more idealistic and naive, or has he grown up having to lie and be deceitful just to survive? If he has followers, what do they think they are getting out of following him? Are they afraid of him? Do they like him, or revere him?
Just some things to think about, I might post here again if I think of anything else. Feel free to ask me about this if there's anything that you want to talk about. ;D