why are only a few small areas dithered? i think the underside of the tail should be darker and i think you could use weighted lines more to your advantage to reinforce the lightsource.
i think the horns make the face a bit unreadable, perhaps make them go backwards more like a rams. I think you've gone overboard with the muscle structure, parts of him look like he's melting. The front left leg should be thinner and the 'ankle' part looks a bit crap.
the thin hairs on the mane need to blend better into the big spikes. the main body lacks contrast compared to the legs furthest from us.
the concept is cool, however you can't really take credit for that, but the execution needs a lot of work. It has potential to go a lot further.