Bird Trio confirmed as Shadow Pokémon, as well as UUs such as Tangela, Farfetch'd.
Shadow Attacks (Shadow Rush, Shadow Wave, Shadow Rave etc.) are Super Effective on everything that isn't a Shadow Pokémon.
Bird Trio have signature moves, Shadow Freeze/Thunder/Fire with high chances of respective status effect.
Codename: XD001 (Lugia) has the signature move Shadowblast, essentially the same as Aeroblast.