The demons are large subterranean humanoids. They are human-like in form and intelligence, and around 8ft tall when stood up. Their face is elongated, with a vaguely canine-appearing snout. They have no eyes, and have multiple stiff quills on their forehead, with the arrangement varying between individuals. They also have beards and head-hair. Their ears are pointed, somewhat like a monkey. Their arms are longer, and they can move on all fours with the same ease as on two legs. Instead of fingernails and toenails, they have what look to be claws. They also have a tail, which is tipped with a set of smaller quills
Their habitat is the underworld, which is a strange set of caves. The underworld is highly radioactive, and quite hot (60°C). It is inhabited by strange, vine-like plants that have adapted to use the radiation instead of sunlight. These are the producers in the ecosystems, and provide food for many animals that dwell in the underworld. The demons, while they originate in the underworld, are capable of surviving and adapting to the Earth-like conditions of the surface world
Do these demons make sense, and could they exist?