The majority of your team will consist of purified Shadow Pokémon. The key to building them effectively lies in understanding their base stats, typing, and potential move pools after purification.

General Purification Strategy:
- Snag Early: Prioritize snagging Shadow Pokémon as soon as you encounter them.
- Heart Gauge Reduction: Keep Shadow Pokémon in your party, battle with them, use 'Call' in Hyper Mode, and utilize the Agate Village massage service and Cologne Case to speed up purification.
- Purify at Celebi Shrine: Once the Heart Gauge is empty, purify them at the Celebi Shrine. This unlocks their full potential.
- TM/HM Usage: After purification, teach them appropriate TMs and HMs to round out their movesets.
Example Builds for Key Shadow Pokémon:
- Shadow Makuhita (Hariyama): A powerful Fighting-type. After purification, evolve it into Hariyama. Focus on physical attacks like Cross Chop, Vital Throw, and Bulk Up (TM). Excellent against Normal, Ice, Rock, Dark, Steel types.
- Shadow Flaaffy (Ampharos): A strong Electric-type. Evolve into Ampharos. Teach it Thunderbolt (TM), Thunder Wave, and Signal Beam (Move Tutor). Great against Water and Flying types.
- Shadow Croconaw (Feraligatr): A reliable Water-type. Evolve into Feraligatr. Focus on Surf (HM), Ice Beam (TM), and Crunch. Strong against Fire, Ground, Rock types.
- Shadow Quilava (Typhlosion): A fast Fire-type. Evolve into Typhlosion. Teach it Flamethrower (TM), Swift, and Thunder Punch (Move Tutor). Effective against Grass, Ice, Bug, Steel types.
- Shadow Bayleef (Meganium): A bulky Grass-type. Evolve into Meganium. Focus on Giga Drain (TM), Synthesis, and Light Screen/Reflect. Good support and against Water, Ground, Rock types.
Always consider type coverage for double battles. Having Pokémon that can hit multiple opponents effectively or support their partner is crucial. Don't be afraid to experiment with different team compositions.