He also played in Elf, consisting of vocalist Ronnie James Dio, keyboardist Mickey Lee Soule, drummer Gary Driscoll, and guitarist David Feinstein.

Gruber was also in the early recording sessions on Black Sabbath's Heaven and Hell album, co-writing "Die Young," until Geezer Butler heard Dio, and returned to the band.

Gruber had also been working on an Elf reunion, even though it seemed unlikely given the deaths of Driscoll and frontman Ronnie James Dio; both of whom had been members of the band from foundation until dissolution.

[citation needed] Early in 2010 Gruber formed "ED3N"- a metal band in the classic rock genre.

The band featured Gruber's former Bible Black bandmate and vocalist Jeff Fenholt and guitarist David Shankle, of DSG and formerly Manowar.