The mysterious Spirit that resides inside the Millennium Puzzle. He helps Yugi gain confidence in exchange of using his body to help others. He can't remember his past so he asks Yugi to go on a quest with him in search of answers.

He helps Yugi through many situations and always comes out victorious. He plays many kinds of Games and uses these Shadow Games to take advantage of his opponents.

After learning about the Duel Monster cards are related to his past, he quickly joins all the tournaments he can to see if he can find more answers to his questions. Eventually he finds out that he was a Pharaoh from Egypt's past.