Mayhem Has the Wildest Story in Black Metal. Somehow, It’s Turning 40.

A few weeks before the pioneering Norwegian black metal band Mayhem set off for a North American tour celebrating its 40th anniversary, the frontman Attila Csihar sounded contemplative.

“The band has, of course, a long history, and lots of things happened,” he said in a video chat from his home in Budapest last October, wearing a necklace of skulls from a Kali temple in India.

As if to prove the point, Csihar, 53, soon underwent emergency surgery, and the tour was canceled. (“Death is the ultimate glorious crown of life, now he understands it even more,” he wrote in a Facebook post.)

Now Mayhem is back on the road (with a New York stop on Monday) to finally deliver its anniversary blowout, this time as the headliner of the Decibel Magazine Tour.

Still, this was all a mere hiccup compared to the group’s extraordinary travails. For fans of extreme music, Mayhem released black metal’s defining album, “De Mysteriis Dom Sathanas,” in 1994. Everybody else might just vaguely remember lurid early ’90s tabloid headlines.

The band, created by a bunch of teenagers in 1984, was starting to make wavelets in its tiny musical niche when its first singer, Per Ohlin (nom de metal: Dead), died by suicide in 1991, at age 22. The first person to turn up at the scene was the guitarist Oystein Aarseth, a.k.a. Euronymous, who posed Dead’s body to snap more dramatic photos. Two years later, Euronymous was murdered by a one-time bandmate, Varg Vikernes. He was 25.