How do you catch Cresselia or just find her? (Platnium)?

Question

Please, I really need to fill up my Pokedex so I can get past the Battle Frontier.

Answer 1

First you have to go into the house that is South of the Gym in Canalave City. There is a young boy in bed and you have to speak with him, the mother and the father. They will ask you to get the 'Lunar Wing'. The father will then show you to his boat where he will take you to an island, I forget the name :P

Here you will go into a cave but she will fly away. She is one of those 'roaming Pokemon' like mesprit of the lake trio. Its a pain to catch without Mean look :D

Answer 2

Cresselia is found by going up to one of the islands (I'm sorry, I can't remember what it's called :P) by going up to Canalave City and asking the Sailor at the ship if we can go there.

Then, you'll be at the island, and inside you'll see Cresselia. You will interact with Cresselia by clicking 'A', and then it will roam Sinnoh. I think that's the way you can SEE it, filling up part of your Pokedex.

You will find an item once you have talked to Cresselia BTW. Pick it up - I think it's a Lunar Wing. (Again, sorry if I'm wrong. I haven't played the game in a while. xD)

Hope I helped. :)