Darkrai, also known as the Pitch-Black Pokémon, is a Dark-type Mythical Pokémon originating from Generation IV, and a member of the Lunar Duo alongside Cresselia. Although in the anime, Darkrai is seen as a hero. In some video games, he is an antagonist who is bent on ruling the whole world of Pokémon and making it a world of darkness. His most important role as a villain is in Pokémon Mystery Dungeon 2: Explorers of Time, Darkness, and Sky, where he is the true main antagonist of the game and he is also the main antagonist of Pokémon Mystery Dungeon: Explorers of Time, Explorers of Darkness, and Explorers of Sky. Though he mainly appears in the post-game plot, he is revealed to have orchestrated the events of the entire game.
In the first half of the post-game plot, Darkrai posed underneath the pseudonym of "Cresselia", adapted her personality and took her appearance, using it to pursue the protagonist and their partner.