One of the most tragic characters in the entire Harry Potter series isn’t even introduced until the very end: Ariana Dumbledore, the younger sister of Albus Dumbledore, who was mysteriously killed during a duel between Albus, his friend Grindelwald, and his brother Aberforth.
Not much is really known about Ariana’s story — however, one Redditor may have just posed a compelling theory about both her life and her death.
So, to backtrack a bit: three muggle boys apparently discovered Ariana performing magic when she was six years old, and they attacked her. The traumatic incident left Ariana mentally and emotionally unstable, and she became terrified of performing magic. “It destroyed her, what they did: She was never right again,” Aberforth Dumbledore says of the incident in Harry Potter and the Deathly Hallows. “She wouldn’t use magic, but she couldn’t get rid of it; it turned inward and drove her mad, it exploded out of her when she couldn’t control it, and at times she was strange and dangerous. But mostly she was sweet and scared and harmless.”
This information leads many Harry Potter fans to believe that Ariana became an Obscurial, which is a creature (explored in greater detail in the Fantastic Beasts and Where to Find Them movie) that is created when a young witch or wizard tries to hide or conceal their powers. As seen in the film, an Osbscurial will frequently experience an uncontrollable outburst of magic (known as an Obscurus) — and it is widely suspected that one of these magical explosions actually killed Dumbledore and Ariana’s mother, Kendra.
When Albus Dumbledore became friends with Gellert Grindelwald, he was 14-year-old Ariana’s lone caretaker at the time (his brother, Aberforth, was still attending school at Hogwarts). Grindelwald and Albus wanted to “take over the wizarding world” together, but Aberforth angrily pointed out that endeavoring to do so would leave Ariana abandoned. A magical duel broke out between Grindelwald, Albus and Aberforth over the issue, and when Ariana intervened she was apparently killed by a stray spell.
Ariana’s death always haunted Dumbledore … and Redditor shazzymcgee’s theory suggests that he was indeed responsible for killing her sister. The theory also suggests that Ariana’s death was responsible for Grindelwald’s obsession with finding an Obscurial, and that Grindelwald was in possession of the elder wand during the duel. As the Redditor writes:
The reason Grindelwald is so interested in controlling an obscurus is because he was overpowered by Ariana.
Ariana is an obscurus, and during the fight that ultimately lead to her death, she was able to overpower Grindelwald and take his wand from him, perhaps in her confused attempt to save Aberforth from the cruciatus curse. In the fight, it was Albus that killed her, which is why he was later able to defeat Grindelwald.
This timeline means that Grindelwald had the elder wand before going to Godric’s Hollow and meeting Albus. There would have been time because Aberforth says that he was “about to go back to school” after they had “known each other a few weeks.” This means that Grindelwald was doing something else at the beginning of the summer after leaving Durmstrang, researching and stealing the wand. He was already aware of the Hallows before meeting Albus so this is possible.
During the fight the elder wand’s allegiance shifted to Ariana, and then to Albus. This is why Albus took so long to fight Grindelwald, he knew that it would confirm that it was he who had killed Ariana. It did, and he lived with that for the rest of his life.
This theory is a bit dense if you weren’t paying super close attention when reading the books, but suffice it to say: Ariana being an obscurus meant she was able to disarm Grindelwald (who theoretically held the elder wand) during the three-way duel, and when Albus killed her, the elder wand’s allegiance belonged to him.
Such a theory would be in accordance with Dumbledore’s lifelong guilt and sorrow over the death of his sister — although it is, sadly, a very dark backstory to one of the most beloved Harry Potter characters.
It seems likely that the future Fantastic Beasts movies will explore this concept/period of history in the wizarding world, so this theory should hopefully become crystallized in time. Until then, we’ll just have to experienced renewed heartbreak over the Dumbledore family’s tragic unraveling, and simply wonder whether or not Dumbeldore really played a hand in his sister’s death …