Black Sabbath bassist Geezer Butler had wanted to embark on a solo recording career since back in the '80s, but the opportunity -- and more importantly, the right group of musicians -- was never provided to the godfather of all heavy metal bassists until 1995 when the musician released Plastic Planet on TVT Records under the moniker of GZR. While many fans might have been unaware of the group's substantial metal lineage due to the confusing name, those in the know were surely sated by GZR's ultra-heavy aggro thrash metal. Joining Butler on Plastic Planet are Burton C. Bell (Fear Factory) on vocals, Pedro Howse on guitar, and drummer Deen Castronovo, whose résumé features recordings from Ozzy Osbourne, Steve Vai, Bad English, and many others. Besides its driving sound, this debut is most notable for the scathing Tony Iommi commentary on the track "Giving Up the Ghost." Never really a live band, this outfit played a few shows with Bell's Fear Factory, and in 1997, Butler released a second disc under the edited (and more recognizable) moniker Geezer. The record was called Black Science and featured unknown vocalist Clark Brown along with Howse and Castronovo. Like Plastic Planet, this second release featured punishing riffs and fine sonic packaging, proving Butler to be an inventive and singularly heavy artist. Eight years then passed before the band returned with Ohmwork.