Returning from Pokemon Colosseum and Pokemon XD: Gale of Darkness is Shadow Pokemon. These are Pokemon who are of the Shadow type and can be caught from trainers with the Snag Machine, although they only belong to Team Xen members.
As their Heart Gauges go down, they are able to regain some of their former moves. Once the Heart Gauge is completely empty, the Shadow Pokemon can be taken to Dr. Jenkel (only once, may fail) or to Eldest in Purify forest to completely purify it. All the Experience it would've gained as a Shadow Pokemon is regained, the Shadow moves are replaced by new moves, some of which it cannot normally get, and it can now learn TMs.
The current list of Shadow Pokemon, along with where they are and their purify moves are:
- Sewaddle - Goldenwood Forest, Will-o-Wisp
- Tympole - Goldenwood Forest, Bounce
- Vanillite - Amethyst Cave, Will-o-Wisp
- Bonsly - Amethyst Cave, Shift Gear
- Tangela - Carotos Mountain, Wild Charge
- Toxicroak - Carotos Mountain, Zen Headbutt
- Girafarig - ___, Flamethrower
- Vivillon - (1st Appearance) Route 3 (Uncatchable), (2nd Appearance) Route 3, Wish
- Ponyta - Shadow HQ, Aqua Jet
- Jumpluff - Route 5, Toxic Spikes
- Feebas - Wispy Laboratory (Uncatchable), Wispy Laboratory Relived, Aqua Ring and Psychic
- Tropius (Uncatchable)