>>32917351I just want a battle with him
Maybe keep the collecting quest, but every time you find 10, Dexio and Sina call you up and give you more hints as to why he's there
After you find 99 of them, you have to catch Xerneas and Yveltal, and then you go to Poni Island to find the last one in that cave and all the others combine to challenge you to prove your worth
Hopefully they tie it into the main storyline with the Ultra Beasts too
