How to Catch Dark Lugia in Diamond

Travel to Pal Park and transfer Lugia from another Pokemon game. In the newer versions of Pokemon, Pal Park is a place on Route 221 where players can import Pokemon from their other games. Without removing your "Pokemon Diamond" game from the Nintendo DS, insert a Pokemon game in which you already have Lugia into the DS' Game Boy Advance slot. Then select Transfer from the "Pokemon Diamond" game. From there, walk into Pal Park and capture Lugia just like you would any other Pokemon. Since the pokeballs in Pal Park never fail to catch a Pokemon, this tactic is easier than catching a Lugia in the wild.

Trade another Pokemon player for a Lugia. To do this, you will need to go to the Union Room in a Pokecenter and either trade with a friend over the Game boy connecting cable or trade over a wireless Internet connection. Once you both have approved your trading selections, you will receive a Lugia in your "Pokemon Diamond" version.

Use an Action Replay cartridge to catch Lugia via cheat codes. The Action Replay cartridge allows players to start off a game by selecting any Pokemon they wish. All you need to do is insert your "Pokemon Diamond" game in the top of the Action Replay cartridge and then insert the cartridge into your Nintendo DS. Then, touch the Star button on the touch screen and select Lugia as a starting Pokemon. This only works for new game files, but it allows you to have a Lugia from the moment the game starts.