From Bulbapedia, the community-driven Pokémon encyclopedia.
Shadow moves (Japanese: ダークわざ Dark moves) are moves known only by Shadow Pokémon in Pokémon Colosseum and Pokémon XD: Gale of Darkness.
Shadow moves have no type and display a blank space where the type would normally go on the summary and battle screens. In Pokémon Colosseum, there is only one Shadow move, Shadow Rush, which has regular effectiveness against any type. In Pokémon XD: Gale of Darkness, Shadow moves are super effective against any non-Shadow Pokémon, and are not very effective against other Shadow Pokémon. Shadow moves cannot receive STAB. All Shadow moves have unlimited PP, and display "--" (two dashes) as their current and maximum PP at all times. Shadow moves cannot be sketched.
In Pokémon XD, the area on the summary screen that would normally display type effectiveness instead displays no icon at all for every type (instead of either a super effective, effective, not very effective, or immune icon).
Damage-dealing Shadow moves can be either physical or special, despite damage categories being otherwise solely dependent on type at the time. Other moves would not be categorized separately from type until the following generation.
Since Shadow Pokémon cannot be traded, these moves are all exclusive to the two GameCube games, with all but Shadow Rush exclusive to Pokémon XD. This also excludes them from use in Contests as there are no Contests in Orre.
All Legendary Shadow Pokémon in Pokémon XD have one of the Shadow moves as their signature move. This move appears as a dark, corrupted counterpart of a move that the Pokémon would normally learn, and has lower base power than its non-Shadow counterpart, but still inflicts more damage due to usually being in a situation where it will be super effective.
||An attack that is so harsh, it also hurts the attacker.
- Shadow moves in Pokémon XD: Gale of Darkness are the only damage-dealing moves which can never deal neutral damage.