After beating the game, go to Pewter City in Kanto and there will be an old man on a hill. Talk to him and he will give you the Silver Feather, which makes Lugia appear in Whirl Islands.
Shadow Lugia is not in HeartGold.
That's only in Pokemon XD
Its Lv.70
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You need Ho-oh and Lugia
yes
no sorry...
You can only catch lugia if you migrated it from firered or leafgreen. If you want lugia get one from heartgold or soulsilver version.
you dont, its not in HeartGold or SoulSilver, Ho-oh (HeartGold) or Lugia (SoulSilver) take their place. You can also get mewtwo
In Heartgold, you can still catch Lugia, only later in the game.
lugia and ho-oh. both can be caught in both soulsilver and heartgold
After you get the silver wing from the old man in pewter city