An international co-production of Italy and West Germany, the film stars Joseph Cotten as Baron Otto Von Kleist, a murderous noble who is resurrected from the dead by his descendant, Peter (Antonio Cantafora), and a college student named Eva (Elke Sommer).

Legend says he burned a witch named Elizabeth Hölle, who cursed him with a spell that would allow him to rise from the dead so she could take her revenge on him eternally.

At the castle, they meet Herr Dortmundt, the entrepreneur responsible for the hotel project, and Eva, a former college student of Karl.

It is an incantation that will supposedly bring the Baron back to life when read in the castle bell tower at midnight.

Eva unties Peter and Karl, and the trio flees from the castle while the Baron's dying screams and Hölle's laughter echo into the night air.

[5] Baron Blood originated as a screenplay written by Vincent G. Fotre, a professional tennis player who dabbled in writing movies.

[4] The screenplay was acquired by independent producer Jerry Briskin, who showed it to Alfredo Leone in hopes he would be interested in co-producing it.

Leone greatly liked the script and saw it as an opportunity to work with director Mario Bava again after their first collaboration, Four Times That Night, had turned out disastrously.

[4] Bava initially turned down Leone's offer because one of the production associates had set the condition that the movie be filmed in one or more of the castles located in Vienna, and he was resolved to remain in Italy.

[14] One week into filming, Baron Blood faced a financial crisis as the Bank of America cancelled their agreement to discount Leone's letter of credit in response to the Nixon shock.

To solve the issue, Leone flew to New York to secure $125,000 from J. Arthur Elliot and Sam Lang, the owners of the independent distribution company Cinevision Films; in exchange, Elliot and Lang received executive producer credits in the English-language version of the film, as well as the US distribution rights to Four Times That Night and Vengeance.

English-language releases credit the story and screenplay solely to Fotre, "adapted for the screen by" another American writer, William A. Bairn.

Leone has stated that the screenplay is almost entirely Fotre's work, and Bava's contributions to it were minor, such as the addition of blood oozing under a door during the invocation sequence.

Wilibald Eser was a fictitious name; the credit was included to satisfy a term of the Italian–West German co-production agreement.

[3] After Leone turned down his pre-distribution arrangement with Allied Artists due to their intentions to book the film only as a second feature, Baron Blood was acquired for release in the United States by American International Pictures, which cut the film by ten minutes and replaced Stelvio Cipriani's score with one by Les Baxter.

[18] It was an international box office success, particularly in the U.S.,[5][19] owing to which producer Alfredo Leone offered Bava a contract for a new film (Lisa and the Devil) and granted him total artistic control on it.

"[20] A.H. Weiler of The New York Times gave the film a negative review, calling the title villain "bland" and stating: "Under Mario Bava's pedestrian direction, the concocted creaking, screaming, gory murders and Miss Sommer's frightened racing through dark passageways largely add up to spectral schlock".

"[23] Dread Central awarded the film a score of three out of five, commenting: "Baron Blood [is] a particularly uneven piece of work; yet, Bava's eye is consistently impressive, creating swathes of Gothic imagery such as a chase sequence through fog-laden streets, sterling use of shadow in framing his antagonist, and a great location in the form of the Baron’s castle.

To be expected is also the director's excellent use of lighting and primary colours, making this another rich visual experience with that distinctly European feel.