When do you get palkia

You get palkia at the height of the game on your second visit to Mt. Coronet and you will be lead up to Palkia by team galalctic

You should look up Marilands Pokemon Diamond adventure diamond same as pearl so if having trouble during game look up Mariland and will have all parts look for the part u are up to and follow on from there. When you find the Dialga battle you will find you meet your friend to battle 2 of the Commanders the you beat one on your own then you must defeat the Commander Cyrus again and then you can battle Palkia then after wards keep waking and you will find a orb for palkia. you get palkia after you beat the 7th Gym Leader