How do you get Diagla and Palkia on Pokemon Platinum DS?

Two ways. The first one is simple, trade them off of DP. The segundo is the basic but harder option. Beat the Sinnoh League, talk to someone in Celestic Town, obtain the Lustrous and Adamant orbs in Mt. Coronet, go to Spear Pillar to obtain these legendary pokemon.

you go to mt conet in a cave in mt cornet there is 2 pokeballs and a rock kia's and collect the pokeballs in them are the 2 orbs (palkia's and diagla's) go the to rock and hit the A button and get the lunar wing go to spear pillar and there will be 2 portals kulay-rosas & blue kulay-rosas is palkia's & blue is diagla's after facing 1 of them go into the cave and go back out and go into the other portal. Be carful they're level 70.

hint)if you dont read the whole message you will fail i now its long but just do it)get both orbs abdamant orb and the listroes oeb(both in a fog room on mt.coronet hearthrome side)make sure you have gotten 8th badge and hm waterfall then go to were you fought/capture girintina on the sides will be one kulay-rosas portal and one blue portal go in whichever you want first but if you want the other one you will have to exit and renter mt coranet o yea before you take the orbs to go get dialga and palkia you will go have to talk to the elite fours champion grandmother in celistic town with the orbs in your invetory she will tell you about the story that happened in alomos town because you werent born yet and after lisenign to her yap on and on then go to mt coranet

You get Dialga and Palkia at the Spear Pillar. And you get dialga and palkia sa pamamagitan ng defeting first Saturn and Mars then you defiting Cyrus and then youl find Dialga and Palkia and then a portal to the Distortion World then a shadow would apear the shadow of Giratina.You would not be to capture Dialga and Palkia because you would be in the Distortion World,but youl be able to capture Dialga and Palkia wen you defet Cinthia.Then you go to the Spear Pillar and then yould find two vortex blue for Dialga and kulay-rosas for Palkia then you go and press the boton A,then you can figth Dialga and Palkia and see if you capture dialga and palkia.

You know how at the Spear Pillar Dialga and Palkia disappear? Well, after you are into the Hall of Fame, go to Celestic town and talk to the elder lady inside the big building. She'll tell you about Dialga and Palkia, then go to the Spear Pillar, and you will see 2 crystals. Those are Dialga and Palkia. Press A to battle Dialga, then go back in Mt. Coronet, and go back to the Spear Pillar, and battle Palkia.

There are four ways.
1st: You get someone to trade with you from the Global Trading Center (or whatever it is called)but that's very hard to do.

2nd: Trade them from your Diamond and Pearl games.
You'll need two DS systems though.

3rd: Buy an AR if you don't already have one and hack...

4th and final way: The simplest way is to beat the elite four and go back to Spear Pillar to catch them. I'm not sure if you have to complete the Sinnoh Dex though first though.

you need rock climb and you need surf and rock smash and you have to go to mount cornet then you see garintina then you have to battle diaga and palkia

Bataling with a realy strong pokemon like mew