THE CRIMSON CULT is a major guilty pleasure of mine. I have a DVD from the UK which is slightly censored and isn't the best quality, alas, but it did come with a great illustrated booklet about the filming.
Karloff got all the best lines and scenes. Michael Gough had a funny role as a mentally compromised factotum.
Barbara Steele's role was almost just a cameo, but her costume was to die for.
G.