Devack

Devack, known as Demak in the Japanese version, is one of the Dark Signers and Roman's right hand man. He wears the black robes of the Dark Signers accented with gold stripes. He has great hatred towards the Signers. His dark mark is the monkey. He frees Greiger from his prison transport, offering him the chance to fulfill his desire for vengeance. He is also responsible for the Minus Curse that infects the Spirit World with the help of his subordinate, Zeman The Ape King. Devack is the only Dark Signer with no background or explanation as to how he died and became one of them, though it was known to be an unwilling transformation.

Biography
It is unknown why Devack joined the Dark Signers as of yet. He appears to have been awakened much earlier, probably making him the second Dark Signer. He first appears out of the Original Enerdy Reactor arriving by helicopter to free Greiger from custody, as his transport guard's souls have been absorbed by Earthbound Immortal Ccarayhua. He then invites him to join them and get revenge on Goodwin for the destruction of his home town. Afterwards they pick up Misty Tredwell and Carly Carmine to return to the Enerdy Reactor.

He finally shows himself to his rivals, the Signers, after Roman's Shadow Duel against Yusei concludes. The battle between them and their rivals as their final battle is about to commence.

Before their departure he shows Luna that he possesses her Ancient Fairy Dragon card, and so in order to get it back she must fight him. Later on, as each one of the Signers is set on defeating their respective opponent, they split up to each of the four control units of the Original Enerdy Reactor. As Luna and Leo are taken by Trudge to where Devack is, she has instead gone into the Duel Monsters Spirit World in order to free Ancient Fairy Dragon from her imprisonment with the the help of her servant, Regulus. However, when Leo finds the control unit, Devack approaches him while the Monkey Geoglyph materializes. Leo then bravely challenges him, stating that if he defeats the Dark Signer then Luna won't have to duel.

Despite Devack's warning that Leo won't be able to save himself and his sister, as he is not a Signer, the duel is still set on. Devack is quickly able to inflict damage to his opponent at the start, but Leo counterattacks with "Power Tool Dragon", his ace card. Demak then Summons the Dark Synchro Monster, "Zeman the Ape King". Eventually, Leo is able to destroy his Dark Synchro Monster, at the exact same time Regulus destroys Zeman in the spirit world, by utilizing his Power Tool Dragon. However Demak summons his true ace card, "Earthbound Immortal Cusillu". He attacks directly, but Leo prevents himself from being defeated. Then, Luna arrives, takes Leo's Duel Disk and the twins duel together.



However, Devack Summons "Ancient Fairy Dragon", and later sacrifices her to prevent "Cusillu's" destruction. This ultimately backfires for him, as Luna uses Leo's "Respect Synchron" to Summon "Ancient Fairy" to her side and uses its effect to destroy "Closed Forest" thus negating all of "Cusillu's" effects rendering it useless. Then Luna assaults it with "Power Tool Dragon", weakening it and destroys it with Ancient Fairy Dragon's attack. At the end, Devack loses.

Regretting his defeat, Devack turns into dust while asking Roman for forgiveness for failing the Dark Signers.



When Rex is defeated in the final battle, and the King of the Underworld is destroyed, Devack is restored to life, along with the other Dark Signers except for Roman and Rex himself. Like his former comrades he is expected to have no memory of being a Dark Signer. At this point, it's presumed he returned to his old life, before dying.

Deck
Devack plays an Ape-themed Beast Deck, in which his Ape monsters can gain an additional Type. The Field Spell "Closed Forest" makes them even stronger, particularly the Dark Synchro Monster "Zeman the Ape King" and his "Earthbound Immortal, "Cusillu". He also had control of Luna's "Ancient Fairy Dragon" card, as well as total control over the seal holding her Dragon's Spirit.