How can you change characters in the different areas, ie, train station, forest, or hogwarts? for example, i need to be a dark wizard in hogsmead station to get an item, but I can't figure out how to change into a dark wizard, I am stuck with the trio. Please Help, this is driving me crazy. Thank You
Actually, you can get Bellatrix sooner after Deathly Hallows Part 2 level 2. Go use Hermione's bag in front of Hagrid's hut in front of the scarecrow and use the pumpkin to fly up and get Bellatrix (Azkaban).
Once you're back at school with Hermione's Bag, Bellatrix (Azkaban) is certainly an option, but you can also get 3 other Dark Wizards much cheaper. Hermione's Bag lets you into the Astronomy Tower. Dolohov and the two Grindelwalds only cost 200,000 studs, where Bella costs 3.75 million.