Well, after your battle where he releases Zekrom, he instructs you to catch legendary Pokemon Kyurem. if completed, N will return to his throne room once every season. His Pokemon change every season, some of his Pokemon even have Dream world ability's!
Instead of writing all of them down, I'll just link you to the page. It will be easier, but the upshot is that he will actually use weather teams with swift swim and chlorophyll users, so he is much harder to beat than last time to bring the appropriate teams for each season.
This is the link.
I hope this helps!