In the main game you will encounter either Palkia or Dialga. They will distort time/space and send you in "sidequests" that allow you to capture the other legendary pokemon. To capture the Zek/Resh they teleport you to the moment after the war when the main dragon is split into three, allowing you to snag them. You capture Ho Oh and the dogs in the burning tower, or Lugia and the the birds during events that resemble the first movie. Screencap this and prepare to bow at the feet of this leakfag