Boggart

 these annoying pests are divided into 3 groups: furry, hall knocker/stone chucker, and ripper. The furry boggarts just turn into animals and aren’t very harmful at all, the hall knocker’s just act as a sort of poltergeist but can turn into stone chuckers who can throw pebbles or even a boulder! And the rippers have a taste for blood and as the name predicts, they rip it from your body.