The "Snag" command is a cornerstone of Pokémon Colosseum's gameplay, fundamentally altering how you acquire new Pokémon. Instead of encountering wild Pokémon in tall grass, you'll often face trainers who use Shadow Pokémon. When an opponent's Pokémon is weakened enough, you can use the "Snag" command during battle to attempt to capture it. This is a critical mechanic, as it's your primary method of obtaining Pokémon throughout the game.
To successfully snag a Shadow Pokémon, you must defeat its partner Pokémon in a Double Battle. Once the partner is down, the Shadow Pokémon becomes vulnerable. You'll need to carefully manage your own Pokémon's health and PP (Power Points) while chipping away at the Shadow Pokémon's HP. When its HP is low enough, select the "Snag" command from your battle menu. The success rate of a snag depends on the Shadow Pokémon's remaining HP and the type of Poké Ball used (though in Colosseum, you primarily use standard Poké Balls for snagging). It's often beneficial to have a Pokémon with a move that inflicts status conditions like Paralysis or Sleep, as this can increase your chances of a successful snag.