Originally released in Italy as The Mask of Satan, but probably better known as Black Sunday, Mario Bava's first feature is arguably one of the finest directorial debuts that cinema has to offer, regardless of genre. While some elements may seem somewhat dated and cliched to a modern audience, I'd say that for the most part it still feels both astonishingly fresh and vivid in its execution, especially for its age. In fact, you could probably even go so far as to call the film timeless, due to its hyper-real, fairy-tale atmosphere.
For those unfamiliar with the plot, it's essentially the tale of a condemned witch (or maybe a vampire; it's never made entirely clear) coming back from the dead to exact her terrible revenge. It seems unnecessary to say much more than that. Besides, it's not really the sort of film to watch for its plot, not that it's bad by any means. To be honest though, even after several viewings, it's one that I find hard to get involved in on that particular level, perhaps due to the (to me at least) almost overwrought, extremely melodramatic feel of some scenes. But viewed as a dreamlike, moving painting, it's completely ravishing.
One of the things which makes this such an accomplished debut is that Bava is one of those rare directors who seemed to emerge fully formed. Indeed, Black Sunday contains many tropes, techniques and motifs that the maestro would frequently re-use throughout his career, such as ruined castles suffused with faded grandeur, themes of attraction/repulsion related to the other, painterly lighting, and ingenious special effects work. As I feel there's little more I can add at present, I'll leave you with a few more examples of the film's exquisite visual splendour.