cmplete the game and go to each cave and try to catch them
To complete the pokedex you only have to see them. However, I would advise capturing them. Azelf has very high attack and speed stats, while Uxie has high Defence and Speed stats. Mesprit is a combination (has around 120 in each stat when you catch it).
YOU CAN CATCH HIM IN LAKE VALOR.BUT YOU HAVE TO CATCH YOUR REGION POKEMON.(PALKIA OR DIALGA).THEN YOU TRAVEL TO LAKE VALOR AND YOU WILL SEE A CAVERN.THEN YOU WILL SEE AZELF IN THE MIDDLE. JTROTTER1295
uxie groudon mesprite azelf and dialga
The only way you can see all the Pokemon on diamond is by going into the GTS and global trade different Pokemon.
the Pokemon was azelf or it could have been mespert or uxie one of those
you have to catch all of the pokemon in diamond or SEE all of the pokemon
Yes, but its for platinum only, if u have all the lake pokemons (Mespirt, Uxie, and Azelf) bring 'em to the cave... Click on the etching of the lake pokemon, and a special pokemon will appear, exlusive for Platinum Only
when you do the veilstone building at the end you see and battle cyrus who is keeping mesperit , azelf and uxie in these chamber things ( in another room ) after you defeat him he gives you the master ball hope i helped :P
A Pokemon
The Pokemon you see do not go in your pokedex.
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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.