you have to trade him from soulsilver or heart gold
You cannot catch Lugia in diamond. you must trade it from Pal Park.
You must trade to get Lugia.
You can't catch a Lugia anywhere in Pokemon Diamond.
You can't catch Lugia in Pokemon Diamond. You can only get it through trading or cheating.
Dark Lugia is also known as Shadow Lugia. You can get it in the game Pokemon XD and it is possible to trade it over to Diamond version.
You cannot get a Shadow Lugia in Diamond or Pearl since Shadow Lugia doesn't exist in the programming of either of the games.
You can purify it to Lugia and then transfer it to Diamond and Pearl.
i think that a dark lugia is just a shiny lugia , you have to get a cheat for that or a heck system
you cant get Lugia in Pokemon Diamond
You can't catch Lugia in Diamond. Unless you migrate one from one of your GBA games or cheat, there is no possible way.
I don't think you can.
It is not possible to get a Lugia egg in Pokemon Diamond. It is generally impossible to get an egg of a Legendary Pokemon the only exceptions being Manaphy and Phione.