From Yu-Gi-Oh!

Ryuji Otogi, known in the English anime as Duke Devlin, invented the Dungeon Dice Monsters game. Otogi also owns a game shop called "Black Crown" that rivals the Kame Game Shop (In the manga, the game shop is owned by Otogi's father, "Mr. Crown"). Duke challenges Yugi Mutou to a game of Dungeon Dice Monsters despite the fact that Yugi does not know how to play it.

In the anime, Duke does this because Yugi defeated Maximillion Pegasus, the creator of Duel Monsters, smashing Duke's dreams of successfully making Dungeon Dice Monsters go world-wide. Duke believed Yugi cheated, and did not deserve to be the King of Games. Using Joey Wheeler (Katsuya Jonouchi), Duke was able to force Yugi to duel for Joey's freedom. Yugi, however, manages to win, using some help from a laptop computer (which Duke included in all Dungeon Dice Monsters set-ups, supposedly to provide help to new players and give accurate statistics) Duke realizes that Yugi plays very honestly, and becomes friends with Yugi. Duke also received information from Pegasus's company that they decided to spread Dungeon Dice Monsters.

In the manga, Otogi is forced to have a Dungeon Dice Monsters duel with Yugi by his father, Mr. Crown, who was cursed by an ancient “Reaching the Goal” dice game he once played with Yugi's grandfather, Sugoroku Mutou. Otogi's father wanted revenge on Sugoroku by doing to his grandson what Sugoroku had done to him. He also wants his son Ryuji to become the new owner of the Millennium Puzzle. During the course of the game, Otogi's father smashes the Millennium Puzzle to pieces. Although Yugi succeeds in defeating Otogi, Otogi's father grabs Yugi and the Puzzle and takes it to a secret room where he attempts to piece the Puzzle back together again. However, doing this causes him to hallucinate about being trapped in a maze, and in his confusion he knocks over a candle, setting the building on fire. Yugi is forced to solve the Puzzle on his own in the burning building, and though he does, he faints, but is rescued by Jonouchi.

Duke/Otogi proves to be a quite important secondary character. Duke saves Serenity Wheeler (Shizuka Jonouchi) and Tristan Taylor (Hiroto Honda) from Rare Hunters in Seto Kaiba's Battle City. Along with Serenity and Tristan, Duke dueled Nesbitt of The Big Five in Noah Kaiba's Virtual Realm. Later, Duke helps Joey when he collapses from his duel with Marik Ishtar, and cheers for Yugi during the Battle City Finals. Duke also helps Yugi, Jonouchi, and Kaiba against the Doma Organization in the Waking the Dragons saga and also tags along during the KC Grand Prix and Ceremonial Battle sagas.

Deck

Duke's first deck is made up of cards that he used in a duel against Joey Wheeler, in which both duelists agreed to open several packs of cards and simply use whatever they pulled from them. All the cards are from the Pharaoh's Servant expansion of the actual card game.

In the Virtual World, Duke's Deck is based around Dice cards and utilizes several monsters he used during his Dungeon Dice Monsters match with Yugi.

In the Waking the Dragons arc, Duke duels one more time, though not much of this deck is seen.

Dungeon Dice Monsters

From Yu-Gi-Oh Card Maker Wiki

Duke Devlin Ryuji Otogi
	English: Japanese:	Duke Devlin Ryuji Otogi
	Attribute:	EARTH
	Type:	Character
	Level:	5
	Card Lore:	Creator of Dungeon Dice Monsters, which apparently went out of style. Pegasus is his idol, and he wishes to become a game designer like him. He also flirts with Joey's sister Serenity.
	Sets with this Card:	Character Cards
	Card Limit:	Unlimited
	Other Card Information:	Gallery - Rulings Appearances Tips - Errata - Trivia Lores - Artworks - Names