"Well, we know that Ariana turned Albus away from a Dark path once," Harry explained. "During the fight with his brother and Grindelwald that led to her death, Albus saw the error of his judgement and turned against Grindelwald to try and protect his family. Ariana's death plagued Albus until his own. Clearly, she has a massive role in his existence. I'm hoping we can find a way to use that ... I just don't know how yet."