Cressila is found on FullMoon Island. After beating the Elite Four, go to the sailor who usually takes you to Iron Island. Inside his house his son is having a nightmare. He will ask you to get a scale to help. He will take you to Cressila. You can't catch it the first time, it will fly away and you must track it down using an app on your poketech.
Same thing for Pearl and Platnium
First, you need to have caught Mespirit, Uxie and Azelf. And then you need to go to full moon island and walk forward a little and then turn right and go in to the trees. After you have done that in front of you you will see Cresselia.
The only way you can see all the Pokemon on diamond is by going into the GTS and global trade different Pokemon.
Type your answer here... It's impossible. Cresselia in a legendary. It won't come in eggs.
you have to catch all of the pokemon in diamond or SEE all of the pokemon
A Pokemon
The Pokemon you see do not go in your pokedex.
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No, you cannot see every Pokémon in the National Dex in Pokémon Diamond however you can see every Pokémon in the regional Sinnoh Dex in Pokémon Diamond.
You see it in the Pokemon league The champion has it
You cannot see it in the wild in Pokemon Diamond; you have to transfer it from FireRed/LeafGreen.
for diamond and pearl there are 150 Pokemon u need to see . in plat nium u neeed to see 210 Pokemon.
u cant see them u see white sparkels and that's where the Pokemon r