Go to spring path and catch Giratina!!!!!!
Actually, this person ^ said to catch Giratina. Well, I caught Giratina when I went to the Distortion World for the first time with my master ball from Cyrus. I don't know what to do either, maybe we should try some site that has Pokemon Platinum Version walkthroughs. Agree?
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You need 21 ultra balls to catch Heatran
you can get them in stark mountin (where you get heatran)
He is in one of those houses in the resort area
Once you catch Heatran you've finished the game, unless you are still to catch Dialga, Palkia, Giratina, Mespirit, Azelf, Uxie or Cressilia. You can also fill in your Pokedex. Basically, the main storyline is complete.
Nothing, you just can't catch him.