Spectre

He was something inhuman. You could look at him and it was like you were looking right through him. That was how he liked it. The more unknown he was the better he could perform. His acts had parts and were laid out. You could think of him as the director of his own horror show. He wasn't careless; he had never been careless. Every detail was planned. The way the weapon was held, the way he acted upon his victim, even the way the body fell. Every slaughter added to his portfolio of violently beautiful art. There were many words to describe him. A masquerader, an artist, a thief.
But, if he was anything he was one of the most skilled men I had ever met. There was no way to prevent him from coming.
You could try, but you would be dead before you even knew he was there. He was something of a haunt. He remained in the shadows unknown till there was work to be done. He would emerge taking lives as he went. He would stop at nothing to make sure the deed was done. He wouldn't stop till he had your blood on his hands. Then, he would leave just as he had arrived. But, this time he would be more elusive and more powerful. None of his victims had made it out. But if they ever had there would only be one way to describe him; a spectre.