Instructions
Play the game in ̶0;Free Play Mode̶1; until you reach the beginning of fourth year. This section is for the Quidditch World Cup.
Head to the right once you start the level. Continue going right until you come across several burning tents and a large boulder. There will be several dark wizards surrounding the tents.
Switch to the dark wizard by pressing the ̶0;C̶1; button continuously until you reach the character that you want. Press the ̶0;B̶1; button to cast a dark magic spell at anything that has the red sparkles surrounding it. For example, there are several boulders with these sparkles.