holy shit jkr had this planned since half-blood prince

hogwartshiddenswimmingpool:

Spoilers for Crimes of Grindelwald ahead: 

In the cave, Dumbledore relives his worst memory. He pleads with Grindelwald to “stop hurting them, hurt me instead” which always seemed out of character for him. He is Albus Dumbledore. He could have fought Grindelwald to save his siblings. 

We know from King’s Cross that at the end of Dumbledore and Grindelwald’s summer together, Aberforth confronts Albus about his neglect of the family. Albus is defensive. Grindelwald and the Dumbledores start to argue, and a fight breaks out. Eventually, Ariana Dumbledore lies dead, and Dumbledore does not know if he or Grindelwald was the one to cast the spell that killed her. 

With the information from Crimes of Grindelwald, it all makes sense!!! 

Dumbledore and Grindelwald make a blood pact that prevents them from fighting each other. When the fight breaks out between them, they cannot harm each other, but Grindelwald can hurt Aberforth (and Ariana) all he wants, and BINGO! Dumbledore is helpless, and can only plead with Grindelwald to stop (hence, his worst memory). In despiration to stop his siblings’ torture, Dumbledore ignores the blood pact, and shoots a spell at Grindelwald, who coutners with one of his own. But neither can attack the other. The blood pact deflects the spells into poor Ariana, who is killed by one of the curses. Dumbledore does not know who fired the spell that killed his sister. 

Beyond that, here’s some speculation: Ariana was sweet and, I imagine, did not start conflict. So if Aberforth confronted Dumbledore, why was Grindelwald torturing both Aberforth AND Ariana (”don’t hurt them, hurt me instead”)?  I think Dumbledore confided in him that she was an obscurial. Grindelwald tortured her by calling out the obscurus, and possibly even trying to rip it from her. If he succeeded, he could have preserved it like Newt did with the one from the girl he met before the first movie. Grindelwald unleashes it in a second-salem orphanage in New York, hoping that it finds another host because “it’s useless without a host,” as Grindel-Graves tells Newt. He then manipulates the obscurial he created into believing they are a Dumbledore. The Dumbledore magic coursing through them and their own tortured soul calls a phoenix, convincing them of the ruse. He tells them they were abandoned by Albus, and he creates the perfect assassin who can kill the one person he cannot.