TV-Series
Description
Devack, known as Demak in the Japanese version, is a character from the Dark Signer arc. He serves as the right-hand man to Roman Goodwin and is one of the primary antagonists confronted by the Signers. His physical appearance is distinctive: a tall, bald man with tanned skin and violet eyes. As a Dark Signer, he wears the black robes of the organization, which are accented with gold or yellow stripes, and he almost always keeps his hood up. His sclera are black, and he has dark red markings running down his face, passing over his eyes. His Dark Mark, the mark of the Shadow Signers, is the monkey.

Very little is known about Devack's life before he became a Dark Signer, as his transformation and death are never explored in the series. It is unclear what events led to his resurrection as a servant of the Earthbound Immortals. Upon his rebirth, he met Roman Goodwin and the other Dark Signers, pledging absolute loyalty to Roman's cause. His primary motivation stems from this devotion, as he shows great dedication to the group's goal of destroying the Signers and the Crimson Dragon. He is portrayed as cruel and condescending, looking down upon those who are not Signers and seeming to take genuine pleasure in the pain and suffering of others.

Devack plays a key role in advancing the Dark Signers' plans. He is first seen freeing the criminal Greiger from a Sector Security transport, offering him a chance for revenge against Rex Goodwin. He is also responsible for infecting the Duel Monsters Spirit World with the Minus Curse, carried out with the help of his ape-like subordinate, Zeman the Ape King. His most significant act is capturing the spirit of Luna's most important card, Ancient Fairy Dragon, and using it as a lure to draw her into a duel.

His role in the story reaches its climax during the battle at the original Ener-D Reactor. While Luna is sent into the Spirit World to rescue Ancient Fairy Dragon, her brother Leo bravely challenges Devack in her place. Devack dismisses Leo as unworthy, as he is not a Signer, but engages him in a duel nonetheless. During this duel, he demonstrates the power of a Dark Signer, first summoning the Dark Synchro monster Zeman the Ape King and then his ultimate card, the Earthbound Immortal Cusillu. The duel eventually becomes a tag-team battle when Luna returns from the Spirit World. Ultimately, Devack is defeated by the combined efforts of the twins, making him the first Dark Signer to fall. In his final moments, he shows his unwavering loyalty by turning to dust and apologizing to Roman Goodwin for his failure. Following the final defeat of the King of the Netherworld, Devack is restored to life alongside the other Dark Signers.

Devack is a formidable duelist whose strategy revolves around Beast-type monsters and the Ape archetype. His key abilities as a Dark Signer include the power to use Dark Synchro Summoning, a sinister alternative to standard Synchro Summoning that uses negative levels. His ace monster is Zeman the Ape King, a powerful Dark Synchro monster. His true signature card, however, is the Earthbound Immortal Cusillu, a god-like creature that can attack directly and is intrinsically linked to his Dark Mark of the monkey.