Cult bands don’t get much more cult-like than Sleep. The metal trio, founded in the early 1990s, has a rare mystique, marked by their major influence on new-millennium stoner rock, their classic albums and their epic record-label feuds (which can happen when you submit one 60-minute song as your album). In the late 1990s, they split – a career move than only enhances one’s myth – only to reform in recent years for sporadic gigs that have drawn pilgrimages by their fans.

On their recent tour, they made Portland’s State Theatre their only concert venue north of New York, and fans journeyed from throughout New England and Eastern Canada to attend. The merchandise table was perhaps the busiest the State has ever hosted – for the entire duration of the evening, the line went at least 10 deep, as fans bought T-shirts until pretty much everything was sold out.

The appeal of the shirts was obvious, as they were adorned with psychedelic artwork of dragons and spacemen that was reminiscent of the comics in Heavy Metal magazine – but in the context of the Sleep’s allure, they were also totems to affirm your allegiance, and prove you were part of one of their rare appearances.

The band opened the concert the same way it opened its 1992 album “Holy Mountain” – with “Dragonaut,” a radio-friendly song fueled by a funky, even danceable riff that does so little to mentally prepare listeners for what’s to come afterward that it almost feels like a sly joke. Once “Dragonaut” faded away, the tempo mostly slowed to a quagmire march, the clear hooks became obscured by smoke and anything else resembling a blues riff was buried under a mountain of sludge.

It was undoubtedly one of the loudest shows the State Theatre has put on in recent years, yet it never felt aggressive or punishing. Oddly enough, and perhaps true to the band’s name, the music was often relaxing. There were people slamming off of one another in a mosh pit throughout the evening and others crowd surfed during some of the more euphoric moments, but despite the potent energy, the music was also contemplative – apt for a band whose vocals are directly inspired by Gregorian chants.

From an instrumental standpoint, the band was as proficient as expected. Al Cisneros found numerous ways to coax sound from his bass guitar, sometimes deftly working both hands up the neck and wildly moving his fingers like a flamenco guitarist, and other times beating the instrument like a drum. There are many bassists with distinctive styles, but Cisneros is one of the few with a distinctive sound, in his case a tone somewhere between a bass and a buzz saw. Coupled with deep chords of Matt Pike’s guitar and doomsday cymbals from drummer Jason Roeder, it created a relentless swamp of sound that could occasionally shift dramatically when Pike would take a high-arcing solo or Roeder would rely more heavily on clean snare hits.

The result of those shifts is that half of the show sounded like dirt was being slowly shoveled on your head, and half sounded like nothing but open spaces and fresh air. There is something unquestionably life-affirming about that duality – there’s little wonder people travel from all over to experience it.

Robert Ker is a freelance writer who lives in Portland.