I've never seen all of this, so i'm happy to find it on Youtube. Essentially, it's a black version of "the Exorcist", so much so that WB sued AIP and they pulled the (very successful) film for decades.
The star of the movie is William "Blacula" Marshall and he dwarfs a lot of his co-stars in this with his gravitas.
Austin Stoker is familiar to Apes fans as he was in "Battle" and the animated series. Carol Speed had a great grindhouse career in the 1970s as well.
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