Dark Yugi is a spirit who resided within the Millennium Puzzle. When young Yugi Moto completed the puzzle, Dark Yugi took up Yugi's body as a host. Occasionally he takes control of Yugi's body to defend him and his friends from bullies and dangerous people by challenging them to dangerous Shadow Games. These games consist primarily of luck based games. Yugi displays a calculated, yet sadistic nature when the game is played, punishing the loser by destroying their mind or other cruel punishment. 