This song is about Aleister Crowley, a British practitioner of black magic in the early 1900s. Known as "The Wickedest Man Alive," Jimmy Page based some of the Led Zeppelin album covers on his work.
It was first released on Osbourne's debut solo album Blizzard of Ozz in September 1980 in the United Kingdom, and then a live version of the song was released as a single in November 1980. The song was written by Osbourne, guitarist Randy Rhoads, and bass guitarist/lyricist Bob Daisley.
The song helped Ozzy play up his mock-Satanic image, which he often did for effect. This his something he did in his band Black Sabbath, who likened their music to horror movies.
Ozzy mispronounces Crowley's last name. It is in fact pronounced with the first syllable sounding like "crow" in English.