Rocker Tony Iommi has given the cancer foundation set up as a tribute to late bandmate Ronnie James Dio a big boost by offering up a one-of-a-kind auction item at an upcoming fundraiser.

The Black Sabbath star, who is himself battling cancer, has donated a priceless Gibson Iommi SG prototype left handed guitar to the Ronnie James Dio Stand Up and Shout Cancer Fund for its second annual awards gala, set for Halloween night in Hollywood.

The axe is expected to go under the hammer for thousands - and to boost the pot, Iommi has agreed to sign the instrument and pose for a photo with the winning bidder.

The Avalon nightclub gala will also feature a performance by Dio Disciples, a supergroup comprising of former members of the band Dio, with a number of prominent rock musicians joining them on stage for an all-star jam.

Among the rockers planning to join the celebrity jam session are Billy Morrison, Glenn Hughes, Frankie Banali, Stephen Pearcy and Joey Belladonna.