It's a voodoo doll, all you have to do is find a strand of someone's hair that you fancy stitch it into the doll, and then voila anything you do to the doll it will do to the person who's hair you snatched. If you want to break the connection throw that dirty doll into the wash.

(This one was a quickie so if any issues arise just throw it in the comments and I'll see what I can change)