What Do You Do After You Have 7 Badges In Platinum?

(i am sorry this is so long) beat the 8th gym. You can do that by going to the top of mount content on the the side left of hearthome town.(you will need the hm strenght and hm rock climb).once you'r there the police dude(only appears in pokemon platinum) will tell you that team galastic has broken trough the wall.then he will give you a black flute.go to spear pillar(top of montain cort.)and go into the Portal to the distortion world with Cynthia find giratina and beat/catch him. Then the guy who was blocking the way to to sunshore city.go to the light tower and talk to the gym leader there than he will leave to his gym. A elite four member will tell you to give him a hot  battle since he beats all the other trainers easy. He isn't that hard.just use some ground type moves to beat him then go challenge the elite four.sorry( this is so long again.)