Just thought I'd say a few things. Firstly, the Satyrs are useful when I'm playing Ljosalfar, way better than those scrawny Archers of Leaves. They're absolutely wonderful for mobilizing a cheap and early war machine; they vaguely remind me of my beloved Jaguar from Vanilla. Secondly, the Freaks are just plain fun, and utterly ingenious. The Balseraphs seemed too dependent upon OO to really work before, but now even after switching to the Order (long story), I had a truly Balseraph trick up my sleeve.
The arena is a great concept, but it's currently too dangerous. Flip a coin and get either get 1 xp or die? Not worth it. While I use it to dispose of "failed" freaks, you should probably either weigh the odds more in the favor of gaining xp, or increase the rewards for survival.
Alternatively, if this could possibly be done and wouldn't be too unbalancing, you could make it so it allows two units to combat each other, with odds and rewards of the sort you'd get if they were hostile units combating each other. It'd be nice to sacrifice my less useful freaks to train the more well-mutated ones: natural selection is always fun. Of course, from what little I know of programming, I can understand if this wouldn't be realistically possible.