The band has since experienced multiple line-up changes, with Tony Iommi the only constant presence in the band through the years. Originally formed in 1968 as a heavy blues rock band named Earth, the band began incorporating occult themes with horror-inspired lyrics and tuned-down guitars. Despite an association with occult and horror themes, Black Sabbath also composed songs dealing with social instability, political corruption, the dangers of drug abuse and apocalyptic prophecies of the horrors of war.BBC Osbourne's heavy drug use led to his dismissal from the band in 1979, after which he began a successful solo career, selling over 10 million albums. He was replaced by former Rainbow vocalist Ronnie James Dio. After a few albums with Dio's vocals and songwriting collaborations, Black Sabbath endured a revolving line-up in the 1980s and '90s that included vocalists Ian Gillan, Glenn Hughes, Ray Gillen and Tony Martin, as well as multiple members of Deep Purple and Rainbow. In 1992, Iommi and Butler rejoined Dio and drummer Vinny Appice to record Dehumanizer. The original line-up reunited with Osbourne in 1997 and released a live album