A few years prior to his reconciliation with the Ozzy Osbourne-fronted Black Sabbath, Tony Iommi started working on his star-studded solo album, Iommi, which came out Oct. 17, 2000. The record, which took almost five years to write and record, included guest vocals by Ozzy Osbourne, Henry Rollins, Dave Grohl, Phil Anselmo, Peter Steele, Billy Idol and others, and it still stands as an in impressive, eclectic and underrated piece of Iommi’s career.

While it might seem like a no-brainer that Iommi would include a track with Osbourne and drummer Bill Ward right before a Sabbath reunion, “Who’s Fooling Who” marked the first time Iommi worked on an original studio song with Ozzy and Ward since 1978’s Never Say Die (Ward last played with Sabbath on 1983’s Born Again).

“Who’s Fooling Who” starts with a tolling bell and a drum fill before bursting into an apocalyptic doom riff. Then Osbourne enters, singing first in a high baritone, then shifting into a more familiar and comfortable tenor as Iommi blasts out yet another classic rhythm. It’s hardly the only keeper on the album. “Flame On,” with The Cult’s Ian Astbury, “Black Oblivion,” fronted by Smashing Pumpkins’ Billy Corgan, “Patterns,” with System of a Down’s Serj Tankian and “Time is Mine,” powered by Anselmo, are all winners.

Interestingly, Iommi adjusts his playing to accommodate the different music styles. “Laughing Man (In The Devil Mask”), which is fronted by Rollins -- features abrupt staccato guitars reminiscent of Helmet, and “Goodbye Lament,” with vocals by Grohl and guitars by Queen’s Brian May, is a hybrid of melodic alternative, electro-rock and downtuned metal. But regardless of what subgenres Iommi explores, he never abandons his signature sound, holding together what might otherwise be a schizophrenic collection of songs.

Iommi co-wrote the album with co-producer Bob Marlette and the guest vocalists, with the exception of “Black Oblivion,” which was penned solely by Iommi and Corgan. Writing sessions for Iommi were productive, leaving the guitarist a multitude of tracks to choose from. Anselmo and Iommi worked on three tracks, including the unreleased “Inversion of the Saviours,” Idol worked on three as well and Corgan guested on two.

In addition to showcasing a who’s who of rock vocalists, Iommi highlights an impressive variety of guest musicians, including Soundgarden bassist Ben Shepherd, Soundgarden / Pearl Jam drummer Matt Cameron, ex-White Zombie drummer John Tempesta and legendary session drummer Kenny Aronoff.

Released in a dark season for metal, Iommi debuted at No. 129 on the Billboard 200 chart. The single, “Goodbye Lament,” made it to No. 10 on the Mainstream Rock Tracks chart, but strangely, “Who’s Fooling Who” was not issued as a single.

Loudwire contributor Jon Wiederhorn is the co-author of Louder Than Hell: The Definitive Oral History of Metal, as well as the co-author of Scott Ian’s autobiography, I’m the Man: The Story of That Guy From Anthrax, and Al Jourgensen’s autobiography, Ministry: The Lost Gospels According to Al Jourgensen and the Agnostic Front book My Riot! Grit, Guts and Glory.