A review of the British horror movie Cult of the Crimson Altar amused me so I'll share the salient paragraphs:
I think I’ve written elsewhere, probably multiple times, about my weakness for horror movies about silly cults, as well as about my fascination with being the strange outsider who is initiated into a circle of wealthy, jaded, and decadent occultists. These are movie occultists, mind you. So all the chicks are hot, the guys are all wearing suits from the 1970s, and everyone has a remote country manor with one of those long tree-lined driveways and a roundabout in front of the house that is partially littered with small sportscars. I come into their midst with naught to my name but a rucksack and a leather jacket, and though perhaps at first they intend to amuse themselves by destroying me, it is I who ends up destroying them, exploiting their jaded nature and turning them against each other — but not before lots of liquor drinking, sordid parties, and sex rituals. All that stands between me and my dream is 1) I don’t think these groups of people exist, and if they do they aren’t calling me, and 2) I don’t know enough about brandy, and the older members of such groups always seem to want to talk about and consume brandy.
My affinity for this myth of the interesting, erudite Eurotrash occultists makes me particularly prone to liking movies about such people. While everyone else is bored to tears, I’m endlessly entertained by movies that consist of lengthy scenes of guys in well-appointed manors leafing through books in the library, or scenes of drunken Satanic revelers stripping down and writhing about to some studio music library version of acid rock. And then if you march everyone down into the cellar to plod about in a circle whilst wearing robes and muttering “Hail Satan” — well, all that nonsense makes me pretty happy. So I can’t argue convincingly against the charges that Curse of the Crimson Altar is full of nonsense and padding. All I can do is shrug and admit that this particular type of nonsense and padding happens to appeal to me.
I suspect the Buffy writers saw this movie and cranked out the Snake Cult at the Frat House episode.