Belial has particularly thick, brown scales. His face has several small horns on it, as well as two longer ones. His wings are very thick.
Many other Dragons have said that Belial is a "worrisome" individual: he speaks in vague, puzzling phrases, often carrying obscure threats. For a while now he seems to have been planning the end of other Dragons, the Wizards, and other powers of the world.
Belial was born long, long ago: he was in fact one of the first Dragons in Mythos.