Shadow-type Pokémon are primarily linked to certain games and special events rather than a standalone type in the mainline series. Shadow Pokémon were first introduced in the GameCube titles "Pokémon Colosseum" and "Pokémon XD: Gale of Darkness." They aren't considered an official type like Fire or Water but instead are regular Pokémon corrupted into Shadow form using dark powers by an antagonistic organization.