|Description||According to the band, the song was inspired by an experience that Geezer Butler had in the days of Earth. Butler, obsessed with the occult at the time, painted his apartment matte black, placed several inverted crucifixes, and put many pictures of Satan on the walls. Ozzy Osbourne handed Butler a black occult book, written in Latin and decorated with numerous pictures of Satan. Butler read the book and then placed it on a shelf beside his bed before going to sleep. When he woke up, he claims he saw a large black figure standing at the end of his bed, staring at him. The figure vanished and Butler ran to the shelf where he had placed the book earlier, but the book was gone. Butler related this story to Osbourne, who then wrote the lyrics to the song based on Butler’s experience.
This song is widely considered to be the first heavy metal song.