Fantasy is a tough genre for movies to get right because it plays into Hollywood’s worst qualities—in bad fantasy, for instance, preestablished rules simply don’t apply when the writer doesn’t want them to apply. Further, fantasy tends to include a lot of destiny, which is the single most-abused crutch of lazy screenwriters, and has a tendency to over-rely on exposition. I haven’t read The Spook’s Apprentice, the novel on which Seventh Son is based, so I can’t tell you if it’s good fantasy or bad. But I can tell you that Seventh Son is bad fantasy, and it’s also a bad movie…