Re: colleseum - miror b, what next.
Alright, basically you have technically finished the game, but not. :p
Next, you go to the 'Snagem Hideout' again.
Okay, if you have caught all your Shadow Pokémon so far, in here you'll find a Shadow 'Shuckle' at around Level 46. So snag him/her and you're done in the Snagem Hideout.
Next, you'll be going back to 'Outskirt Stand'. Where you'll catch your final Shadow Pokémon: 'Togetic'.
After that, you've finished really.. Unless you wanna do one last thing. Go battle 'Justy' again, and get TM27.
And if you don't know how do get 'Ho-oh', purify all your Pokémon and then finish: 'Mt. Battle 100 Trainer challenge'.
Thats all you need to know really, hope it helps, man....