Devack Devack , known as Demak in the Japanese version , is Roman Goodwin ' s right - hand man and a member of the Dark Signers . He freed Greiger from his prison transport , and offered him the chance to fulfill his desire for vengeance . He was also responsible for the Minus Curse that infected the Spirit World with the help of his subordinate , Zeman The Ape King . Design . Appearance . Devack wears the black robes of the Dark Signers that were accented with yellow stripes . His dark mark is the monkey . Personality . Devack had great loyalty to the Dark Signers ' cause and to Roman in particular . His final words were an apology to Roman for losing . He also looked down on those who were not Signer s , and enjoyed the pain of others , as seen when he tried to show Luna more sadness by using " Ancient Fairy Dragon " against her . Biography . It is unknown how Devack became a Dark Signer . At some point upon his rebirth , he met Roman and the other Dark Signers , and pledged his loyalty to Roman . At some point , he was given Ancient Fairy Dragon by Roman to set up his eventual confrontation with Luna . He appeared out of the original Ener - D Reactor by arriving by helicopter in order to free Greiger from custody with an " Axe of Despair " card , as his transport guard ' s souls had been absorbed by the " Earthbound Immortal Ccaryahua " . Devack then invited him to join them and get revenge on Rex Goodwin for the destruction of his hometown . They later picked up Misty Tredwell and Carly Carmine from the destroyed Arcadia Movement building and returned to the Ener - D reactor . He finally showed himself to his rivals , the Signers , after Roman ' s Shadow Duel against Yusei concluded . Before their departure , he showed Luna that he possessed the " Ancient Fairy Dragon " card , and so in order to get it back , she must fight him . Later on , as each one of the Signers was set on defeating their respective opponent , they split up to each of the four control units of the Original Ener - D reactor . As Luna and Leo were taken by Trudge to where Devack was , she instead went 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 found the control unit , Devack approached him while the Monkey geoglyph materialized . Leo then bravely challenged him , and stating that if he defeated the Dark Signer then Luna wouldn ' t have to Duel him . Despite Devack ' s warning that Leo wouldn ' t be able to save himself and his sister , as he was not a Signer , the Duel was still on . Devack was quickly able to inflict damage to his opponent at the start , but Leo counterattacked with " Power Tool Dragon " , his ace card . Devack then Summoned the Dark Synchro Monster , " Zeman the Ape King " . Eventually , Leo was able to destroy his Dark Synchro Monster , at the exact same time that Regulus destroyed Zeman in the Spirit World , by utilizing his " Power Tool Dragon " . However Devack Summoned his true ace card , " Earthbound Immortal Cusillu " . He attacked directly , but Leo prevented himself from being defeated . Then , Luna arrived , and took Leo ' s Duel Disk and the twins Dueled together . However , Devack Summoned " Ancient Fairy Dragon " , and later sacrificed her to prevent the destruction of " Cusillu " . This ultimately backfired for him , as Luna used Leo ' s " Respect Synchron " to Summon " Ancient Fairy " to her side and used its effect to destroy " Closed Forest " thus negating all the effects of " Cusillu " and rendering it useless . Then Luna assaulted it with " Power Tool Dragon " , weakening it and then destroyed it with " Ancient Fairy Dragon " . The Duel ended with Devack ' s defeat . Regretting his defeat , Devack turned into dust while asking Roman for forgiveness for failing the Dark Signers ( In the dub , he tried to drag Leo and Luna with him to the Netherworld , but failed when Yusei came in and saved them ) . When Rex was defeated in the final battle and the King of the Netherworld was destroyed , Devack was restored to life , along with the other Dark Signers except for Roman and Rex himself . It is unknown if he kept the memories of his time as a Dark Signer . Non - canon appearances . Yu - Gi - Oh ! 5D ' s Tag Force 4 . In " Yu - Gi - Oh ! 5D ' s Tag Force 4 " Devack appeared as a Partner character and could only be found at nightfall after completing Luna ' s story . Yu - Gi - Oh ! 5D ' s Duel Transer . In " Yu - Gi - Oh ! 5D ' s Duel Transer " , Devack was found on the fourth floor of Bifrost . If you have " Earthbound Immortal Cusillu , he appears without his cloak . Beating him unlocked his Deck Recipe at the card shop and enabled the player to continue Dueling him in Free Duels . Decks . Devack played an " Ape " - themed Beast Deck . His " Earthbound Immortal " card was " Cusillu " .