Many of the Shadow moves are dark, corrupted counterparts of a move that the Shadow Pokémon would normally learn, such as Shadow Lugia's Shadow Blast, which, like the move Aeroblast, sends a high-powered stream of air at the foe, and can only be learned by Lugia. These moves often have lower power than their non-Shadow counterparts, but still inflict more damage due to being super effective. Their usefulness is also increased by their lack of PP, as they can be used as often as needed within a single battle.
Damage-dealing Shadow moves can be either physical or special, despite damage categories being otherwise solely dependent on type at the time. This distinction appears to be based on the types of the moves they are most similar to; for example, Shadow Blast is a physical move because its counterpart is a Flying-type move, which are all physical in Generation III. Other moves would not be categorized separately from type until the following generation.
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. 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.