Wikipedia
Freischütz
A Freischütz (" freeshooter"), in German folklore, is a marksman who, by a contract with the devil, has obtained a certain number of bullets destined to hit without fail whatever object he wishes. As the legend is usually told, six of the magic bullets (German: Freikugeln, literally "free bullets"), are thus subservient to the marksman's will, but the seventh is at the absolute disposal of the devil himself.