It's..OK
But that's all. The shading on those flat rocks is very off, in fact, it took me several minutes to realise that the one on the right WAS flat. The castle in the background looks dreadful. It has no perspective at all, and looks really flat, maybe add a little bit of an angle to it.
The anatomy also is dreadful. The guitar guy's head is too big, and his legs and feet are too small. The other guy's arms are too big and his head is too small, and his shoulders are at a weird angle, making him look a little...off.
Apart from the castle and the anatomy, the line art is very good, and the most part of the shading is too, but the colours bug me a little, particualrly the purple on the guitar. It jumps out a bit too much and draws away from the whole feel of it, perhaps tone down the saturation. The other guy's skin colour is also a bit odd, it's very grey, and doesn't look right. However, I DO like the red of the fire around his hand. Very vibrant, and without lines, which really brings an impact into it. If I were you, I'd switch the colours on the guitar and the purple fist. I think it would look a whole lot better if the only really saturated section were the flames of their attacks.
The piece as a whole is OK. Nothing special, nothing dreadful. I've been focussing more in this review about what you can fix, rather than what is good, so I don't think it's completely dreadful. However, I do think that you could really do with making a few changes to it.