As based on Edgar Allen Poe's Danse Macabre, Castle of Blood is an eerie, atmospheric chiller than succeeds on all fronts. The film relies on the marvelous black & white visuals, genuine atmospheric tension, and the strength of its leads, as opposed to cheap scares or graphic violence. So if you're only interested in gore, then Castle of Blood won't suffice, as it is a more refined, unsettling kind of horror picture. The castle itself is ideal for such material, with a constant menace thanks to its interiors, though I'm sure the superb photography enhanced those elements. And of course, Barbara Steele simply controls the screen here and makes it impossible to take your eyes off her performance. Castle of Blood has all the elements in place, with a gorgeous lead, great source material, and a gifted director, plus it packs an ending that satisfies. This is the kind of release that makes horror fans tremble, as Synapse Films has pulled out all the stops and issued the definitive release of a genre classic. Antonio Margheriti's eerie epic Castle of Blood has never been given a proper release, but Synapse has not only struck an all new digital transfer in anamorphic widescreen, but also restored scenes that were removed for the American theatrical release. In other words, this is a top notch effort in all respects and as such, I commend Synapse and give Castle of Blood a most high recommendation.
DVDAuthority

Less about plot and more about atmosphere, the movie moves at a slow and dreamlike pace, with a lot of long and lingering camera movements full of creepy and creaky old set pieces and populated with melodramatic characters. The most obvious comparison for the movie is Mario Bava’s Black Sunday, and while there are certainly a few similarities, Castle of Blood isn’t really that close in any other regard than the fact that the two films have Ms. Steele in a lead role…
While not really a good film as a Poe adaptation, Castle of Blood is still a great gothic horror film with a wonderful cast and some of the best atmospheric camera work to come out of 1960s Italy.
Not recommended for those who need countless amounts of gore or action to keep a movie interesting, but for those who appreciate atmospheric chills and nightmarish visuals, there is more than enough to appreciate.
DVDManiacs