Black Sabbath have always been able to tap into the dark side, but we wonder exactly how the music will sound that was written while guitarist Tony Iommi was going through chemotherapy sessions for lymphoma treatment. The guitarist recently finished his treatments, but says that the physically draining sessions didn't deter him creatively.

Gigwise reports that Iommi told Kerrang, "It was good for me to do that. I did feel tired and sick and it does make you sick, you start throwing up. But on the days when I felt I could do it, we were all there working." Ozzy Osbourne and Geezer Butler left the U.S. and relocated the writing sessions to England to accommodate Iommi's treatment, and the guitarist says that was a huge boost.

Butler recalls, "[Tony] was going to the hospital one day and we'd go into the studio the next depending on how the chemo was affecting him." Apparently the treatments didn't slow Iommi or the rest of the band too much as Ozzy Osbourne recently revealed that they had already penned 15 songs for their next album and expect to write a few more before things are through.

Iommi recently admitted he was nervous upon returning to the stage in their hometown of Birmingham last month, marking the band's first performance back. However, the guitarist made it through an entire show okay, and will proceed with this weekend's headlining performance at the 2012 Download Festival as well as the band's August date at Lollapalooza.