Here's a note on surviving the battle after this acquisition. ;)
Don't be scared by the new big ugly that appears. He's actually a babe once you get to know him. And definitely get to know him first, because he'll help you out. Remember the B button finishing moves? This guy will provide this twice before expiring on you. Each time you end up taking a ride with him, he'll start swiping at everybody around him... and you, taking out some of the trash for you.
And you'll need this move. Though he comes out solo, he'll soon be joined by those evil panther-like demons along with some foot soldiers. So pound him silly first, ride him and let the good times roll!
I think you have limited control of him. At least you can nudge him towards a direction you want. But the swiping is all up to him so ride him when the enemies are more clustered. His swipes will be much more effective.
For times when you can't ride him, dodge his charges and claw swipes. Use your AOE blast ability a couple of times (those are especially effective on the panthers) and get those B finishing moves in on the others whenever you can to thin their numbers.
This party will have a rerun. So just do the same for the second wave and you'll be in the clear!