Roots of Freak of Nature

Mabel was a Danish pop music group from Stenløse, Denmark. They came to prominence after winning the Dansk Melodi Grand Prix song contest with the song "Boom Boom" in 1978, and represented Denmark at the Eurovision Song Contest the same year. The band were successful in Denmark and Spain. Mabel later became the metal band Studs, and disbanded in late 1982. Lead singer Mike Tramp went on to form White Lion in 1983.

Helloween is a German power metal band founded in 1984 in Hamburg by members of bands Iron Fist, Gentry, Second Hell and Powerfool. The band has at times been called one of the most influential European heavy metal bands of the 1980s. Its first lineup consisted of singer and guitarist Kai Hansen, bassist Markus Grosskopf, guitarist Michael Weikath and drummer Ingo Schwichtenberg. By the time Hansen left Helloween in 1989 to form Gamma Ray, the band had evolved into a five-piece, with Michael Kiske taking over as lead vocalist. Schwichtenberg and Kiske both parted ways with Helloween in 1993; Schwichtenberg died two years later as the result of suicide. Between then and 2016, there had been numerous line-up changes, leaving Grosskopf and Weikath as the only remaining original members. As a septet, their current lineup features all of the surviving members of the Keeper of the Seven Keys lineup, in addition to the remaining members from the Keeper of the Seven Keys: The Legacy-era.