after you beat the E4 you can talk to Cynthia's grandmother and she will show you a picture of the legendary pokemon to complete you Sinnoh Dex. she'll show you Dialga in Pearl and Palkia in Diamond

U need to get it wi-fi after seeing it from cynthia's grandmom put up a casscoon or silkcoon u will get it after about a day from chienese people!!! OR trade it from diamond

Get it from Diamond (trade) or you can look at the book Cynthia's Grandmother has. She has the book after you capture, defeat, or flee from Palkia. You don't have to wait until you beat the Pokemon League

Get it from Diamond (trade) or you can look at the book Cynthia's Grandmother has. She has the book after you capture, defeat, or flee from Palkia. You don't have to wait until you beat the Pokemon League

i had a lvl 100 shiny dialga but it was so weak so i traded it