Hades was a very vain being, though you may figure that out by seeing how he only considered himself and two gods who worked under him as worthy of being in Elysium. He didn't want his body to be hurt, so he used a human vessel whenever he went to battle. That also meant that killing the vessel didn't serve to stop him for long by itself, he hided his real body deep in Elysium, where it was safe.

[Until they barged in, achieved the eighth sense, went through barriers that they shouldn't have been able to cross and impaled him with Athena's staff. Of course.]

His real body was pretty normal, he looked like any human, a very handsome and perfect one, I suppose. I'm not really a beauty critic. The most impacting traits in him were his eyes, for someone so cruel, vain and selfish his eyes were very clear and sad. Just by them one would have thought he would be a pure soul or something like that. He had long black hair, one of the darkest shades I've ever seen, even here, blue eyes and a very white skin. And, of course, he looked as if he had never even lifted a spoon to feed himself because others did that for him.