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 in at first. In the Japanese version, 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.
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".
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 nosiest and ugliest card 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 Cards. 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 final opponent.
On a replay game, it is possible to face him as Nitemare, whose God card will have maxed-out stats.