How are the Dementors Created?
Dementors are some of the creepiest and scariest things in the Harry Potter series. We know that the tall, black-hooded figures can suck the soul out of a human’s mouth by “kissing” them, that they force people to recall horrible memories, give their victims the feeling that they’ll never be happy again, and that the one charm that repels them is a Patronus Charm. One thing that has never been mentioned, however, is how to create or comepletely destroy a dementor.
Dementors are not in Fantastic Beasts, so we don’t have the background information like do for creatures such as bowtruckles and nifflers. This also means that dementors are “beings” or “has-beens,” not “beasts.” Dementors have never been known in the books to speak, so why are they not classified as beasts? I believe that dementors join the ghosts in the “has-beens” category.
My theory is that dementors are created when people pass through the veil in the Department of Mysteries. They die and return as dementors. If dementors are created in the veil, that would also explain a lot about why JK Rowling was so torn up about Sirius dying: he is now what Harry fears most. I think that the only way to destroy a dementor is to force it through the veil with a patronus or another as yet unknown method of controlling dementors. When a dementor is destroyed, it releases the souls it has consumed back into the world, and the dead person comes out through the veil, possibly alive, since JK won’t say if Sirius comes back. The whispering on the other side of the veil are the souls the dementors have taken.
I know it sounds far-fetched, but JK has surprised us before. Anything can happen in this series, and though it’s perhaps doubtful that dementors are somehow created and destroyed through the veil, nothing’s impossible. Just think of the implications on Harry if it were true!