Notable for the teaming of horror icons Boris Karloff, Christopher Lee, and Barbara Steele - but unfortunately it's a fairly routine 60s British occult potboiler with a predictable plot and touches of dated psychedelia. The presence of Karloff and Lee provides some much needed weight, but Steele is painted green and relegated to a few uninspired dream sequences. Modestly entertaining, but ultimately forgettable.
The best things about this film were Barbara Steele in a wicked costume, Boris Karloff saying "Instruments of torture." *scare chord*, and an angry man with antlers wearing a tiny leather bikini. Sadly, they are very few and far between.