When Welcome to Night Vale first launched as a twice-monthly podcast back in 2012, the premise seemed simple: a radio presenter relayed the news from a small desert town in south-western United States, rich with the local colour you'd expect from a community radio station – that is, if your neighbourhood were populated by mysterious hooded figures and faceless old women who secretly lived in your home. When attempts to describe Night Vale inevitably fall short, well-meaning comparisons are drawn. Imagine NPR broadcasting from the Twilight Zone or Twin Peaks, in its transformation of terror into the mundane: a place where a god-like glowing cloud of noxious gas can become president of the school board.

'The fun thing about Night Vale as a writer is it's less of a story and more of a world,' says Joseph Fink who, alongside Jeffrey Cranor, created Night Vale and writes the majority of its episodes. 'It contains multitudes of places and characters that each have their own stories to tell, so there is this almost infinite number of stories we can explore within the fictional world we created.

Indeed, whereas its compatriots in horror have stuck mainly to its original medium, Night Vale has spawned a complex universe told through a multitude of forms. The podcast is now one of the most downloaded in the world, and has spun off into two novels, an upcoming television show and several live shows – the latest of which, titled A Spy in the Desert, is coming to the Edinburgh Fringe.

credit: Hunter Canning

How do they navigate Night Vale's transition onto the stage, considering that people are used to experiencing the podcast as an aural and solitary event? Indeed, it's a different beast altogether, says Cecil Baldwin, voice of Night Vale's radio host Cecil Palmer. 'In the podcast format, it's just you and a microphone, and it's very intimate,' he says. 'But what's great about performing in front of two hundred people is that there's no fourth wall between you and the audience, so we can play around with the idea that the audience is listening to a radio show, when in reality, they're sitting with a bunch of other people, looking at a performance. It takes those tropes and plays with them in a really fun way that you can't do on a podcast.'

'Telling stories through different media allows us to use their inherent styles to explore stories we couldn't tell in other forms,' adds Fink. 'For instance, the novels allow us to tell longer stories that are outside the point of view of our podcast's narrator. And the live shows allow us to incorporate the audience into the stories in a way that we couldn't on a pre-recorded podcast.'

Much of Night Vale's success has been due to the richness of its storytelling, brought to life by Baldwin's baritone delivery of Fink and Cranor's scripts. As a relatively new medium, the podcast is seen as an exciting platform for experimenting with the limits of storytelling. For Baldwin, it's every performer's dream. 'For people who work in more traditional theatre, the play is what it is – you run it for a week or two years, but it's always the same thing. The wonderful thing about Night Vale is that room for new material, to try new things and test your creative brain. Every episode has new problems to solve, and it's a great way to stay in shape as a performer.'

It's this very sense of creative experimentation that makes Night Vale and the Fringe a natural marriage of the minds, says Baldwin, who first performed at the Fringe in the Neo-Futurists' production of Too Much Light Makes the Baby Go Blind back in 2014. 'The Fringe honours and values new work, work that isn't always big budget theatre,' he enthuses. 'They value creativity and creative problem solving, and that very much fits in with Night Vale's aesthetic.'

The conversation soon turns to Night Vale's political bent. Beneath the town's manifold terrors has always existed a sharp political edge – corruption, authoritarianism and corporate overreach exists in Night Vale too, beneath the guise of the monstrous and the fantastical. Rather than being a tool of deflection or a purely stylistic choice, however, Baldwin suggests that it is exactly this surrealist approach that allows Night Vale to dive into the heart of heavyweight issues.

'What's great about fantasy and sci-fi is that you can say more about the world that you're living in by using metaphors, or by using characters that represent the real world,' says Baldwin. 'Often the message becomes even more powerful, because we're not talking about Donald Trump, we're talking about Pamela Winchell, or the Sheriff's Secret Police. It allows people to bring their own reality to the podcast, rather than us doing the work for them.'

As Night Vale is a place where all conspiracy theories are true, which theory do they wish were real? Baldwin laughs. 'I still feel like there's something involving Trump, like a video tape of him saying horrible things that Putin probably has. It's sort of wishful thinking. One of the great things about Night Vale's absurd humour is that it reflects just how absurd the world we live in actually is.'

'Numbers stations,' says Fink. 'But the good news is those are real.'

Welcome to Night Vale, Summerhall, until 26 Aug, 1pm, 3pm, 11pm, £35.