I found this movie a little disappointing because I fell for the original advertising and was under the impression that 70's cult actor Andrew Prine would be playing a Manson-like cult leader. Instead Prine's character, Simon, is an actual warlock, although obviously not a very good one since has to live in the LA storm sewers. He also doesn't have much of a cult, just one dumb kid who follows him around like a puppy. At one point he does seduce a rich politician's daughter, but he is mostly interested in using her to cast a spell and has sex with her only as an afterthought. There is also a surprising homosexual subtext for a movie made at that time (although it is balanced out with abundant female nudity).
The movie is really only half-serious. The tone is often pretty campy. Prine is good, but he often seems to be poking fun at his own character. He is actually much more entertaining when he plays these kind of characters straight. Technically, this is probably a better movie than "Centerfold Girls", "Nightmare Circus" or other Prine vehicles, but I still maintain Prine would have made a great Charles Manson.