Zeon (Zeno in the English version) is a mamono who bears an uncanny resemblance to Gash Bell, except for his paler colors and purple eyes. His spells mirror Gash's but are notably more potent; unlike Gash, Zeon remains conscious during spellcasting, allowing him full awareness of his actions. His cloak possesses magical properties, enabling him to shield himself and his bookkeeper from harm and teleport them to different locations. He is exceedingly powerful, malevolent, and harbors intense hatred towards humans, particularly Gash.
Dufaux (Dufort in the English version) serves as Zeon's bookkeeper. Characterized by his silence and emotional reserve, Dufaux also exhibits psychic abilities. It is later revealed that Zeon is Gash's twin brother and the cause of Gash's amnesia. Their father, the king of Makai, possessed the ultimate power known as "Baou," which was passed down to Gash. Fearing for Gash’s safety and the potential jealousy of his brother, their parents sent Gash away to live as a commoner while Zeon underwent rigorous military training. Upon discovering both his brother and the "Baou" power, Zeon grew resentful, leading to his participation in the Mamono Fight with plans to secure victory and ensure Gash's suffering.
In pursuit of this goal, Zeon found his bookkeeper and tracked Gash to a forest in England, where he mercilessly attacked Gash, stripping him of his memories instead of burning his book, thereby forcing Gash into a life of confusion and isolation in the human world. Gash was subsequently found by Seitaro Takamine, who sent him to Japan, hoping Kiyomaro could uncover Gash’s origins and benefit from their interaction.
Zeon became intrigued by the immense tower Faudo, having researched its latent powers. After extensive preparations, he manipulated events to awaken Faudo using Gash, intending to usurp control once it was active. Successfully defeating Riou and taking over Faudo, Zeon enhanced its capabilities, empowering its guardians and previously allied mamono. This set the stage for a formidable challenge against the remaining mamono, culminating in a showdown with Gash and Kiyomaru.
In both manga and anime versions, Zeon’s book is ultimately burned following a fierce battle between Gash’s Bao Zakeruga and Zeon’s Jigaridasu Uruzakeruga. In the anime, Zeon remains resentful, breaking Faudo's control jewel out of spite. In the manga, however, Zeon realizes the hardships Gash faced and regrets his actions, leading to the jewel's destruction due to the strain of their fight. As twins, their father's original power was divided, with Zeon transferring his share to Gash to complete Bao and defeat Faudo.
In the original Japanese version, Zeon is voiced by Urara Takano. In the VIZ Media dub, Zeno is voiced by Debi Derryberry, who also voices Gash.
