It’s simple, really: no Black Sabbath, no heavy metal. The Birmingham quartet may have risen from the British blues-rock boom of the late ‘60s, but their sledgehammer riffs and bulldozer rhythms exuded an apocalyptic aura that spawned a whole new kind of devil’s music. The doomy tritone riff that opens their 1970 self-titled debut pried open the crypt leading to rock’s netherworld, summoning the inimitable voice of Ozzy Osbourne, who traded the chest-puffing, girl-crazy machismo of the typical hard-rock frontman for the dread-ridden delivery that could only come from a working-class kid raised in a no-hope industrial town. Black Sabbath’s bleak outlook was ultimately a reflection of the world around them: The blistering title track to 1970’s Paranoid provided an unflinching admission of mental illness that was virtually unheard of in rock music at the time, while the immortal “War Pigs” was a more damning indictment of the Vietnam War than anything coming out of the hippie movement. But guitarist Tony Iommi and bassist Geezer Butler packaged these dark thoughts in the sort of riffs that were so infectious, they practically qualify as pop earworms—the most tone-deaf hesher could blurt out “duhn-duhn DUH-NUH-NUH” and you’d instantly recognize it as the intro to eternal stoner anthem “Sweet Leaf.” After Ozzy’s substance-abuse issues forced his ousting in 1979, Sabbath recruited glass-shattering vocalist Ronnie James Dio for two albums (Heaven and Hell and Mob Rules) that anticipated both the fearsome velocity and theatrical flamboyance of ‘80s metal—and presaged decades of rotating members, reunion tours, and parallel line-ups. But in 2013, Ozzy teamed up with Iommi and Butler for their first album together in 35 years, 13, a chart-topping, Grammy-winning comeback that proved, for all their imitators and offshoots, there can be only one Black Sabbath to rule them all.