He is a demon who is the archduke of the underworld and one of the main characters in the series. Stolas has a calm and collected personality, often using his intelligence to outsmart those around him. Despite his demon nature, he is shown to have a sense of honor and justice. Stolas is an anthropomorphic owl demon. He is tall and slender, with a white, heart-shaped facial disk and small black beak, resembling that of an owl. He has two pairs of almond-shaped red eyes, one set atop the other.