Ethnina (キョウ＝エスニナ), also known as the Book Hero, is one of the Vassal Wielders from Glass' World. He carries a dark and gloomy aura around him. Kyo has white hair with a silvery sheen. His eyes are described as stagnant and rotten, comparable to the eyes of a dead fish. He wears a long coat while wearing a strange belt around his chest, which is full of test tubes. He is described looking either like a scientist or an alchemist. Kyo fancies himself a genius. A rampant egomaniac, whenever his opponents make mistakes, he will repeatedly call them stupid, yet he makes use of his attacks in extremely simple and easy-to-see-through ways. Also a megalomaniac in his quest for more power.