When playing Harry Potter Years 5-7, I noticed there are things only Wizards with Dark Magic can interact with. I figure these are things I will have to go back and do later, as right now I don't have anyone in my party that can use Dark Magic.
Which characters in the game use Dark Magic? Who is the first one I can unlock, so that I can go back and get whatever it is from these areas?
If the DS version is the same in this regard, it would be Bellatrix (see this question for location).
On the DS version if thats what you're playing I would go for Alecto Carrow on price. You can also get Dolores Umbridge for the same reason she is cheap. But if you do have a lot of money to spend its Tom Riddle or Bellatrix LeStrange. Just a note.
Peter Petigrew is good because he is cheap. He costs about $20,000.
Actually, Umbridge isn't a dark wizard. You don't need to buy a dark wizard, because in the 5-7, once you unlock the Polyjuice, it already comes with the four Hogwarts founders, and one of them (Salazar Slytherin) is a dark wizard.
Now, you must know that the dark magic is allowed only at the "Back to Hogwarts" phase, in Part 2 of year 7. Right before you enter this phase, you may try to use Slytherin for dark magic, and it will work. After that, it's just important to have a key character, like Griphook, Bogrode or Ms. Cole, and a strong character, like Arthur Weasley (he can fix muggle objects), and you are able to explore the hole game.
I already did 100% of both 1-4 and 5-7.
