Like most demons, Koros bear a resemblance to their master. They are tall, handsome demons with crowns of horns, long black hair, and feathered (or sometimes bat-like) wings. They are capable of taking a human form, which they use liberally.
Koros encourage pride and envy in mortals, advising them to ignore, push aside, or destroy others because they are lesser beings, and because their pride leads them to believe that they deserve whatever they want and can take, no matter the cost. They enjoy taking the form of an advisor or close friend to an egotistical human, preferably one of great power, in order to whisper suggestions into their ear, goading their egos in order to push them into greater and greater sin.
The demon-kin children of the Koros, often very comely and well aware of it, are noteworthy for their bright green eyes and long, curled horns.