In Southern Sweden a giant round rock lies on flat farmland, and the lovely story my ancestors used to tell to explain how it got there came down to this: a troll threw it there. As evidence,in a nearby castle, one can find a horn and a pipe that come into the story. The horn contained what today would be called chemical weapons, which burned the back of a horse when the hero of the story was smart enough to dump it over his shoulder rather than drinking it. Man and horse got away by riding across the furrows of a field, because everyone knows that trolls must run back and forth the full length of each furrow, which slows them down tremendously. The facts all fit. Some fringe conspiracy theorists may question the very existence of trolls, but such arguments need not be taken seriously.