He woke up in bed one night in 1969 to see an indefinable creature at the foot of his bed, and later recounted the experience to bandmates Ozzy Osbourne, Tony Iommi and Bill Ward about it.

Butler says in a new interview: "I woke up in a dream world and there was this black thing, staring at me. It just lasted a second, but it freaked me out. I told Ozzy, Tony and Bill about it - it was pretty scary at the time. I think that's what inspired Ozzy to come up with the lyrics that open the song: 'What is this thing that stands before me?'"