Quote Originally Posted by Diego Havoc View Post
That's new. How do they affect the game? Do you have to start over from the beginning?
When activated, they increase/decrease the difficulty; in challenge mode (hard mode), the trainer Pokemon are higher level, with better movesets and more AI intelligence (so I'm told), and I think trainers may sometimes have more Pokemon as well. (Conversely with easy mode obviously.)

The pain the arse is that you can't get the keys until you beat the E4, and as I understand it, you can only share them over IR or local connections and not the global link. As I understand it, once you have the key, you can change the difficulty in the main menu, so it can be changed at any point.

Incidently, just in case you may not have heard, if you have a Black or White game (preferably post E4) you can do something called Memory Link, which means you can link up that game to your BW2 game, and get flashbacks and such (and the events in BW get referred to with that game's trainer's name and such). That data is independant of your saved game (again, accessed through the main menu), so you can do it during or before (like I did) even starting a game. I think I recall something about being able to do memort link of the wireless network, but you'd have to check to confirm.

(Bulbapedia/Serebii are worth checking out for all this, as they have more details than I have and are likely more correct.)