Obscuri (Obscuruses?) are described on the wiki as

the repressed energy of a child, known as an Obscurial, who is forced to repress their magical talent through physical or psychological abuse.

Usually this becomes a large black blob which kills the Obscurial and people near him/her. My question is--is this what happened with Ariana Dumbledore? She was obviously magical in some way, but her power was suppressed--everyone thought she was a Squib.

Aunt Muriel says of Kendra

Kendra died before Ariana — of what, nobody ever seemed sure

and Aberforth says this of Ariana:

“It destroyed her, what they did: She was never right again. 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."

It seems to me that what happened was that for some reason, Ariana became an Obscurial, and this power killed Kendra and later, herself. It maybe that this was why

Grindelwald was so interested in the Obscurus in the first place, since he witnessed her death.

Obscuri (Obscuruses?) are described in the wiki as

the repressed energy of a child, known as an Obscurial, who is forced to repress their magical talent through physical or psychological abuse.

Usually this becomes a large black blob which kills the Obscurial and people near him/her. My question is--is this what happened with Ariana Dumbledore? She was obviously magical in some way, but her power was suppressed--everyone thought she was a Squib.

Aunt Muriel says of Kendra

Kendra died before Ariana — of what, nobody ever seemed sure

and Aberforth says this of Ariana:

“It destroyed her, what they did: She was never right again. 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."

It seems to me that what happened was that for some reason, Ariana became an Obscurial, and this power killed Kendra and later, herself. It maybe that this was why

Grindelwald was so interested in the Obscurus in the first place, since he witnessed her death.