Saturday’s sunset has long gone, but there’s so much UV paint glowing in Bristol nightclub Lakota that I feel I might end up with a tan from it. A throng of ravers throw shapes while a shamanic selector, flanked on stage by two dancers, pumps out squelchy beats. Colourfully daubed faces light up with joy and arms swirl into spacey lasers, ready to break through into a different dimension. For one night only, I am an initiated member of the Tribe of Frog, a Bristolian club night that’s been putting on mind-boggling parties like this for the last 25 years.

To mark the occasion, the team has gone mad as a box of proverbial amphibians with the kaleidoscopic decor, but the soundtrack is the same as ever: psytrance. This is a 135bpm-plus, four-to-the-floor, knowingly melodramatic, multi-layered offshoot of trance with mesmerising refrains and epic drops. Tristan Cooke, a DJ and legend of the scene who speaks to me a week before the party, explains that it “grew out of partying on beaches and nature,” specifically amid the trance scene in Goa, India, in the early 1990s. He says that psytrance enhances the effects of LSD. “It’s about attempting to achieve a peak experience. In a nutshell, it’s spiritual raving.”

Chris Rana, co-founder of Tribe of Frog, never made it to Goa but he did travel across Thailand in the 90s, where he and his late wife Donna (whose artwork continues to adorn the night) fell in love with psytrance. “For the first time in our lives, we found this feeling of freedom,” he says in the Tribe of Frog green room.

Back in Bristol, they started a nightlife decor business called Wildfrogz together. Why frogs? “It’s always considered a mystical animal because it can exist in two worlds, in the water and in the air,” Rana says. They met Jason Frog, as he’s known, on a job. “You can get into this plateau of bliss, where you’re dancing to this synchronised rhythm,” Jason says of his beloved genre, while munching his way through a bunch of bananas. After getting a gig kitting out a psytrance party in London called Enlightenment, they decided to throw their own.

Tribe of Frog was born, with its opening night taking place in August 2000. “Every inch of wall space is covered in psychedelic banners, projections, lights and all that is just simulation to trigger the overload of the senses,” Cooke says, adding that even as a veteran DJ, playing Frog still smacks his gob: “It’s about creating a Garden of Eden in a club.” Transcendent outfits were also encouraged from the outset, with Jason explaining that “the concept has been that if you create a super-real environment, people forget their worries because they’re in this other world that their mind creates for them”.

Since then, Tribe of Frog has hopped across the globe and spawned a residency stage at Hampshire’s Boomtown festival. At a pub round the corner from Lakota, before the night begins, I bump into a group of twentysomethings in hand-crocheted frog hats who all met at Boomtown as solo punters. “If you put that much care and dedication into making something a tradition, you’re going to create a following,” says Matthew Sarrington, as another friend pulls up his sleeve to show a frog tattoo.

Despite its widely dispersed fandom, though, Tribe of Frog is still somehow quintessentially Bristol. It’s true that it lacks any of the edge of the drum’n’bass, trip-hop or dubstep that seemingly wafts out of every concrete orifice and car window in Stokes Croft. Yet it encapsulates the left-field spirit of the city, in one way or another.

For other people, however – who are obviously not here tonight – psytrance is a relentless headache, even musical torture. Dance music fans often file it next to other oft-scorned niche genres such as happy hardcore and donk, seeing psytrance as a woo-woo scene beloved by crusty ravers sporting harem pants and scarfing too much magic mushroom chocolate.

“Psytrance has always been the black sheep of the dance music fraternity,” Cooke admits. “They see it as a bunch of unclean-dreadlocked, culturally appropriating hippies. But it’s becoming part of the mainstream.” It’s true that psytrance, now far removed from its roots and attracting tens of thousands of revellers to festivals such as Boom in Portugal, has faced criticisms of cultural appropriation, amalgamating and whitewashing eastern iconography.

But it’s an intricate issue. “Some criticisms remain valid, but every instance of ‘cultural appropriation’ should be carefully scrutinised,” says anthropologist Graham St John, the author of Global Tribe: Technology, Spirituality and Psytrance. “Sometimes, the othering in question is primitivist and even outright exploitative. Other times the borrowing and recognition is respectful and mutually beneficial.”

For those who aim at creating the latter, it’s a way of life, and there are always new tadpoles to join them. In the smoking area, I bump into Francesca Stevenson, an emerging psytrance selector (as Cheska Onyx) who won a competition to play tonight. “It’s not just about hearing it, it’s about feeling it,” she says, connecting psytrance’s local appeal to the south-west’s ley lines.

Elsewhere, freshers-week students with constellations of glitter and gap-year tunics abound, many telling me, wide-eyed, that this is paradise. “The Frog has always just had this bottomless pool of young people,” Rana says. He also says that there have been many “frog unions” over the years – I’m told that Cliff, who plays the drums at Tribe of Frog, met his partner at Tribe and is bringing their daughter along for the first time tonight.

Around the club I overhear talk of trust funds, and discourse around the psychedelic drug 2C-B, and all of this – plus of course the psytrance itself – may put people off. But there are genuinely no posers or chinstrokers at Tribe of Frog. Mad, fun dancing is encouraged and there are multiple generations all going for it under one roof. “It’s a cool, funky, safe, amazing place … people are not going there to try and get laid. It’s about partying together,” Cooke says.

The mind expansion, and sense of community, has been a lifesaver for some people. “It healed me. It brought me out of my shell. You get a better perspective on yourself,” Jason says. But while there can be individual catharsis, it’s always about the collective. Rana’s mantra, shared with me earlier, echoes in my mind as I float out of Lakota back towards Bristol coach station: “Here, you always drop your ego!”