I don't often encounter that form of punctuation. We would have been in deep trouble at school if we started using dashes instead of proper punctuation. Its use seems widespread these days and occasionally I admit I use it myself, feeling lazy as I do so. I think it occurs mostly in poorer quality writing, the book-of-the-film sort of thing. Americans seem to use it more.
Maybe it is legitimate in some sentences but I have no dea what its point is in the one you provide.
Hi, Elisa98, This is from the Harry Potter books, right (describing a Dementor)? I agree: dash —, not hyphen – (see under Special Characters (the Greek letter 'omega' in the line of icons at the top when you post), although all keyboards have a key for -.
(P. S., A dash is sometimes called "an em dash", and a hyphen, "an en dash".)
I used to work at a place where they created fonts and they actually had rulers that were marked in pica and elite (font widths). That was the only time I've ever been able to tell a hyphen from an en-dash from an em-dash, and even then, I didn't care about the difference.