I love both films. I had the pleasure of seeing Black Sabbath on the big screen at a Bava film festival years ago. It's an anthology; the best of the three segments is A Drop of Water, but the others are good too. If you wanna see the great Barbara Steele, the Goddess of Gore, playing a 75-year-old serial killer, The Butterfly Room (2012) is worth a watch. Has cameos for Joe Dante and a bunch of 80s scream queens as well, which is fun.