You only get 1 Master Ball in the game, so I suggest Mesprit or Cresselia because they run away after you throw 1 PokeBall. Their harder to catch, so keep using 1 attack at a time and wear them down. To get Dialga, he's at the top of Mount Coronet. You can find a walkthrough to get through. Azelf and Uxie, you only have 1 try, so have lots of Ultra Balls, Great Balls, have Pokemon that can shock them and freeze them and you should be good. To find out where to go, check out this AWSOME Pokemon site: www.serebii.net. I hope that I helped!
the legendary Pokemon in diamond and pearl are dialga and palkia.
No, a Bidoof cannot evolve into any Legendary Pokémon in Diamond.
Heatran
a lot of legendary Pokemon
Dialga
you cant unfourtanately
arceus
you can't catch it because you already beaten the legendary
no
you can't unless you have AR
Empoleon is not a legendary Pokemon. It is the final evolution of Piplup, one of the starter Pokemon in Pokemon Diamond, Pearl, and Platinum.
That would have to be Dialga.