Btw his Charizard has Charizardite Y and his Mewtwo has Mewtonite Y.
either from a pokemon event that gives it out or you have an Entei, Raikou or Suicune and go to the Lostlorn Forest and fight the pokemon that looks like a legendary (be sure to have lots of pokeballs).
Well I've played through Black many many times and you can only fight Ghetsis the most important Sage of the 7 he has powerful Pokemon like Bouffalant and Coffifrigaus So powerful he is Stronger than the last battle against N at level 50's or 60's be prepared I recommend if you don't want your Pokemon to all faint level 60-70 you should get a well balanced team with Defence Attack Sp. attack Sp. Defense Speed and hp Ice Types and Water Types are a little big help But expacilly against Hydriegon But the last. Battle with N is Tuff He has Zekrom Zoarark Archen's last evolution and the water rock turtle's last evolution (forgot it's name) Ghetsis has a electric type N and Ghetsis are the only ones you should worry about - Krystal the Ace Trainer of eeveeloutions