Brains have a lot of protein.
This is a boss character I would enjoy. Very gothic, divine, and frightening. I really think that to start off, I'm going to say that the background helps sell this character. The red, blotchy piece makes him seem evil, and the fade to white keeps it interesting while preventing it from pulling away from the focus of the picture. It's an excellent effect with such a dark character. His limbs give him a vibe of rising from the darkness of the earth. The headdress gives a sense of divinity, dominance, and pure power. the chest and shoulders make it seem that he was once human, and a dark corruption washed over him and turned him into a monster. It seems like the armor fused to his flesh. This makes me wonder what kind of boss he would be. Would he hold a giant, epic sword? Would he be a great warlock character that chanted spells with his hands and the bowl of brains? I think that his style wouldn't fit a hand to hand fighter because of his helmet.... wing.... face. I don't know what to call his head, but that piece makes him seem like he's more than a brawler.
That was the good stuff; let's talk about the bad (or should I say, the questionable). Sometimes the darkness of his form makes certain areas on his body confusing. I'm not really sure if he has legs, if he's fused to the earth, if he's part statue, if he has hooves, etc. Why do I say that? At around the hip area, he looks like he has two distinct legs. However, at the foot level, I can't really tell what's going on. It looks like there could be two "hooves", or that he's fused to the earth (but I think the ink around his feet kind of removes that question). The darkness just makes it a bit confusing there, so I would recommend widening his stance or something. Even if he was part goat and had his legs pointing inward to an extreme, his foot wouldn't be directly in front of the other. The other think that bugs me is his hand that's holding the head. There are a bunch of tentacles coming from it. Where are those coming from? I can't tell because of the steam coming from the head. It makes that part of the picture confusing and take a lot more close observation. Generally, the smaller things in this picture spell "Epic" to me. When I look at the head, I feel more confused. I'm not really sure how to fix that. Maybe make the brains less steamy. I am giving you a ten though, so don't treat what I'm saying as an attack. Just my thoughts.
All ranting aside, I think that this piece is really beautiful and dark. Castlevania, Shadow of the Colossus, and other games with really sweet, dark, deep detail really appeal to me. I love the bosses from those games, and I almost felt bad for killing some of them. That's how I think I would feel after slaying this guy. I just wanted to give you a mood state if someone asked how to portray this guy. I don't think he would need to talk. Maybe just sit upon a dark throne, and when the hero comes in, he just stands and gazes downwards. Shriek darkly when he's wounded. Maybe even be a final boss. Anyways, great work.