La bestia debe morir

Others commenting here seem to have been distracted by the "game" aspect of the movie, which was, of course, a gimmick added after the movie was finished.

Although the story really required a larger budget, this well-cast, intelligent horror thriller is well worth watching. The story is reasonably suspenseful, the direction good enough most of the time, and it is unusual in depicting the central villain as someone who LOVES being a werewolf. It's based on a good novel, which was given reasonably respectful treatment.