Evil Without a Face

Once a small peaceful town. One which could be described as idyllic. The, out of nowhere an entity arrives. a monster which cannot be describe, evil, horrible, criminal, everything you cannot imagine.
It thrives on chaos, mayhem, rape and torture, and no one can help.
Can it be destroyed? One would have to capture it first.
No one knows where it lives as it brings horror and disappears until its next heinous performance.