uhhhhhh---- ma'am, a black hole like that wont just delete the air and create a vacuum---- it'd cause a large and violent implosion as the surrounding air goes rushing in to fill the gap in space------- thats DANGEROUS ON MORE LEVELS THAN YOU REALISE
She could have just said that she "hunted monsters to make her territory safer," but this is probably better.
@tomonoshi To be fair, that basically did happen, and she did activate it a decent distance away.
It's a bit weird that it was called "Black Hole," though, as it's more of a vaporizing effect than a real black hole. But, the name does match the description, so it makes sense for a fantasy world with little knowledge of space.
"Dark Void" probably would have been a better name, though.