For a full article, head on over here: http://nuggetbridge.com/articles/new-mechanics-introduced-vgc-2016/
Basically: Xerneas, Yveltal, Zygarde, Groudon, Kyogre, and Rayquaza are all legal now. Which is pretty fucking stupid considering that Mega Rayquaza is the most op Pokemon in fucking history.
Bullshit. Personally, I just think that all legendary Pokemon should be banned, but hey, what do I know?
Every fucking winning team in 2016 is going to have a Mega Rayquaza which will make it not fun and game play will be shit. I can't wait.