Fans of Dio know that exploring his early work means traveling to the other side of the rainbow. "Rainbow" was the name of Dio's first big band, a heavy metal outfit that began as the pet project of Deep Purple guitarist Ritchie Blackmore, then continued to evolve throughout the '70s and '80s, rotating through a long series of members and musical styles. Their fan base came and went and came again, largely because the band covered so much musical ground, often alienating the fans they had earned with their previous record. But for the most part, they're considered a hard-rock staple of the '70s that any true fan is well-acquainted with.

Rainbow came together when Ritchie Blackmore tired of Deep Purple in the mid-'70s, announcing to the surprise of many that he was quitting the band and starting fresh. He teamed up with Ronnie James Dio, who had earned a flowering cult following for his melding of medieval fantasy and metal in his former band, Elf. They formed Rainbow in 1974. They debuted a year later with Ritchie Blackmore's Rainbow. The cover featured a shimmering castle and a rainbow curving over it. The age of "dragon rock" had arrived.

But it was the following year's release, Rising, that made them a hit. That record took the best of Blackmore, Dio and the band's then current lineup, and turned it into something that filled arenas when they went on a successful tour promoting the album.

They released a live album and 1978's Long Live Rock 'N' Roll shortly thereafter. By that point, Dio wanted to strike out on his own. He left the band in '79, and it steadily lost its fanbase by becoming more derivative. The continual loss of band members made it extremely hard to stay viable, and the band eventually disbanded in 1984.