Regular demon eyes, but stuffed with red-hot fire souls. This makes them much more powerful and efficient, but at the cost of their appearance. They outer layer of the eye is melting and rotting due to the intense heat of the soul, and disfiguring the rest of the eye. They have a much higher drop chance for black lens, because their lens is in the process of being charred black.
Nevermind, apparently getting fire stuffed into you is actually a trend for Demon Eyes and a symbol of prestige. Go figure.