A person in Pewter City will give you the Silver Feather, then go to Whirl Islands. When you get to the end of the cave you will see Lugia.
Chat with our AI personalities
You need Ho-oh and Lugia
You will need to trade from HeartGold or SoulSilver or migrate Ho-Oh or Lugia from a Gameboy Advance game in order to be able to have Ho-Oh or Lugia in Pokemon Pearl.
I mean…do you want Pokemon HeartGold? The difference between HeartGold and SoulSilver is that you catch Lugia in SoulSilver and Ho-Oh in HeartGold. Other than that they’re the same thing. You need a DS, DS Lite, or 3DS to play it though. It’s not playable on any other console.
In heartgold, Lugia is obtainable at the Whirl Islands but u need to obtain the silver feather from a guy in Pewter City. Once u have that silver feather, u can go deep into the Whirl Islands and find Lugia.
In Pokemon Heartgold you need Ho-Oh before going to the Elite Four/Pokemon League so I am sure it's the same for Pokemon Soulsilver.