Nitemare Nitemare , known as Card Majin ( カード魔神 " Kādo Majin " , Card Demon God ) in the Japanese version , is the main antagonist in a few of the " Yu - Gi - Oh ! " video games . He has a less powerful form , DarkNite , which he usually appears as at first . In the Japanese versions , DarkNite is referred to as " Card Majin " , while Nitemare is referred to as " Card Majin ( true form ) " . A majin is a malevolent deity that causes misfortune and disaster . He appears in " Yu - Gi - Oh ! Dark Duel Stories " , " Yu - Gi - Oh ! Forbidden Memories " and " Yu - Gi - Oh ! The Falsebound Kingdom " . Manawyddan fab Llyr is the " Yu - Gi - Oh ! The Duelists of the Roses " incarnation of Nitemare and claims to be his brother . Kazuki Takahashi included line art for Nitemare , along with other rough sketches for cards for the real life card and video games in " Yu - Gi - Oh ! Duelist " volume 11 . Appearances . " Dark Duel Stories " . In " Yu - Gi - Oh ! Dark Duel Stories " , DarkNite is the only stage 4 opponent . He is unlocked by defeating all stage 3 opponents , at least five times each . Nitemare is a stage 5 opponent , unlocked using the password " 43504084 " . " Forbidden Memories " . In " Yu - Gi - Oh ! Forbidden Memories " , Nitemare is known to be the creator of the Shadow Game s . He is sealed away in the Forbidden Ruins , only to be awoken when the 7 Millennium Items are brought there . When Heishin awakens DarkNite , he attempts to order him claiming it is part of the pact , but Darknite says that he does not recall making a pact with Heishin . When Heishin begins to plea with DarkNite , he quickly grows tired of the conversation and turns Heishin into a card . Finding it to be the noisiest and ugliest he ever created , DarkNite burns it saying it doesn ' t deserve a place in his Deck . DarkNite then turns to the prince and Seto saying that they would make nice additions to his Deck . Seto reminds the prince about the Millennium Item Card s . The prince then holds out the cards forcing DarkNite back . Unable to fully hold him back , the prince is left to duel DarkNite . After losing once DarkNite refuses to accept his defeat and turns into Nitemare demanding another Duel . The prince proceeds to defeat Nitemare , sending him back to where he came from . " The Falsebound Kingdom " . In " Yu - Gi - Oh ! The Falsebound Kingdom " , DarkNite is the final boss . He is described as a " dark spirit , " who is turned loose by Scott Irvine after the hero ( either Yami Yugi or Seto Kaiba ) dismantles Irvine ' s virtual world , The Kingdom . Although DarkNite has only one monster , it is one of the powerful Egyptian God Cards . Which god card is faced depends on the hero , and seems to correspond to the God each hero has the most rivalry with ; Yugi faces " Obelisk the Tormentor , " and Seto faces " Slifer the Sky Dragon , " After defeating him , The Kingdom is shut down once and for all . DarkNite doesn ' t appear in Joey ' s storyline , since it is a prequel to Yugi ' s storyline , where he faces Marik , who uses the " The Winged Dragon of Ra " , as his final opponent . On a replay game , it is possible to face him as Nitemare , whose God card will have maxed - out stats . Deck . Darknite and Nitemare use a Labyrinth themed Deck . Nitemare uses Gate Guardian and the monsters who composite him : Kazejin , Suijin and Sanga of the Thunder , as well as spells such as Raigeki or Change of Heart .