From Bulbapedia, the community-driven Pokémon encyclopedia.
Purification, or "opening the heart's door", is the only known method of changing a Shadow Pokémon back into a normal Pokémon. It is used in Pokémon Colosseum and Pokémon XD: Gale of Darkness to restore any Shadow Pokémon that Wes or Michael have snagged. Purification can be seen as a main goal in those games.
Purifying a Pokémon
Before completely opening the door to a Shadow Pokémon's heart, its Heart Gauge must first drop to zero, turning completely white.
The following actions will slowly open the door to a Pokémon's heart:
- 0% Purified: This is the state at which a Shadow Pokémon is snagged. The Pokémon has at least one Shadow move, and its Nature is unknown. Before any progress has been made on the Heart Gauge, the Pokémon's description will state, "The door to its heart is tightly shut." After any progress has been made, until the next stage, the description will state, "The door to its heart is starting to open."
- 20% Purified: When at this stage, the Shadow Pokémon will relearn its first non-Shadow move. Until the next stage, the description will state, "The door to its heart is opening up."
- 40% Purified: The Shadow Pokémon's Nature is revealed (though it was determined when the Pokémon was first encountered), and the Pokémon will also start receiving experience points in battle, though this is not mentioned to the player or counted towards a level-up until the purification process is completed. Until the next stage, the description will state, "The door to its heart is opening wider."
- 60% Purified: The second non-Shadow move is relearned. Until the next stage, the description will state, "The door to its heart is nearly open."
- 80% Purified: The Shadow Pokémon will enter Hyper (or Reverse) Mode more frequently. Also, in Colosseum only, a third non-Shadow move is relearned. Until the next stage, the description will state, "The door to its heart is almost fully open."
- Empty Shadow Bar: The Shadow Pokémon's heart is 'ready to open' and the Purification process can be finished, turning the Shadow Pokémon back into a normal Pokémon. At this stage, the description will state, "The door to its heart is about to open. Undo the final lock!"
Once a Pokémon's Heart Gauge is completely white, it is time to "undo the final lock," the final step in opening the door to a Shadow Pokémon's heart. This is done through a Purification Ritual. In Pokémon Colosseum, Purification Rituals can only be performed at the Relic Stone in Agate Village, but in Pokémon XD: Gale of Darkness, they can also be performed in any Set of the Purify Chamber at Pokémon HQ Lab as well.
In Pokémon Colosseum, the player can find up to three special items called Time Flutes to instantly purify any Shadow Pokémon by summoning Celebi at the Relic Stone, which will open the door to a Shadow Pokémon's heart. Time Flutes do not appear in Pokémon XD: Gale of Darkness.
Shadow Lugia is a special case and can only be purified if it is put into one of the Purify Chamber's Sets when all nine slots have achieved maximum tempo. Its Heart Gauge will also reset if the process is interrupted, such as by removing Shadow Lugia from the chamber.
Once a Pokémon is purified, any Shadow moves are replaced with other moves. In Pokémon XD, besides moves learned through level up, TM or breeding a just-purified Pokémon will know at least one special move. It immediately gains any Experience and Effort Values that it has earned in battles prior to the purification, meaning that it may gain one or more levels. The Pokémon receives a special Ribbon for "clearing all difficulties", and at this point the Pokémon Trainer may choose a nickname for it. The player is now able to trade the purified Pokémon with the GBA games Pokémon Ruby, Sapphire, Emerald, FireRed, and LeafGreen using a GameCube/GBA cable.
The following Pokémon can only gain certain moves if they are a Shadow Pokémon purified in Pokémon XD: Gale of Darkness: