Warg!

[juggernaut]

This is so easy that any idiot with an APE can do it. Just take a hyena, make it about ten times as large as normal and make it to where it prefers hilly grassland with a little savannah and maybe even a few gray and brown rock patches (Just make it like New Zealand). Now if you could make it feed on the dinosaur steaks that t-rex's get that would make it lean and mean. Also the savannah grass would likely be it favorite foliage but any thing from The grasslands would likely do. It would actually be the perfect animal to go with the stone walls since that would look like Isengard. Oh and get rid of that stupid annoying laughing and replace it with bear noises and maybe a few wolf sounds.