There’s something about the way the ancient buildings in the oldest quarters of Sibiu, now part of Romania, cast shadows across the wetness on uneven roads making it easy to imagine horse-drawn carriages clattering their way to some castle in the distance. Even on a Saturday afternoon, downtown Sibiu feels strange when, around lunchtime, the streets suddenly become deserted. Shops shut en masse, bars and restaurants are deserted, and the only sign of life is the odd stray dog, slightly menacing and padding about.

Where, incomers may wonder, has everybody gone? It’s as if following some inaudible signal known only to natives, everyone moves indoors, perhaps to take part in some ancient rite away from prying eyes. Or maybe, just maybe, they’re scared of the light, however dulled by the drizzle it may be. Because, come early evening, as if by magic, everyone is there again, going about their merry way on a Saturday night busy enough to resemble any other city in the European Union that Romania joined in 2007.

Such paranoid ruminations may be the curse of only knowing the Transylvanian terrain by way of schlocky Hammer horror films in which Dracula rises from the grave, again and again. In this instance, however, it’s probably more to do with the mighty presence of Faust, Silviu Purcarete’s epic staging of Goethe’s soul-selling poetry, which was the centrepiece of the 2009 Sibiu Theatre Festival in June.

Just as Bram Stoker’s fictional Count was transported to Britain, Romanian-born Purcarete and his company of more than 100 performers are getting ready to ship the spectacle for dates at Ingliston’s Lowland Hall – the only venue large enough to accommodate the show – as part of Edinburgh International Festival. Audiences here should prepare themselves for the most magnificently unholy of theatrical communions.

How it will work when audiences are bussed out to Ingliston during the early evening remains to be seen. In Sibiu, however, where everything only ever seems to happen after dark, it’s a strictly late-night affair. Taken to an abandoned and dilapidated factory on the sleepy outskirts of town, the audience is unfazed by the seemingly ramshackle nature of the event, which starts inconspicuously enough, as a man in a white suit moves through the audience and tears down a thin stage curtain.

What he reveals is an old school classroom, with a row of desks on bare floorboards flanked by big bay windows. Scattered on the floor is a pile of discarded newspapers, the leftover detritus of acquired knowledge. At the desks sit a blank-eyed array of students staring at open laptops bombarding them, one presumes, with images and information that have bamboozled them enough so that they resemble demented inmates of Bedlam. Their teacher, Faust (played by a dome-headed Ilie Gheorghe, whose make-up renders him grotesque and Nosferatu-like), is left impotent and alone, his passion for the innocence of girl-child Gretchen, here played by several young actresses, left troublingly unspoken.

When the devil comes calling in the sprite-like form of actress Ofelia Popii, who appears from a very un-CS Lewis-like wardrobe after a black dog goes inside, Faust willingly goes to hell and back in search of enlightenment. What follows, as the audience too are led into a crowded and chaotic world of flying angels, rutting pigs, Dionysian rites, sacrifice and ceremony, is an astonishing sensory overload of sound and vision that signals, as Mephistopheles attempts to woo Faust in Purcarete’s reading, one of the most primeval courtships ever set down and made flesh.

Purcarete’s work is nothing if not elemental. The night before, a cast of 28 – small by Purcarete’s standards – had performed his version of Ovid’s Metamorphosis, spending much of the show’s two-hour duration in two feet of water in a purpose-built swimming pool. It was the insistence of the rain that had accompanied the performance to make it even wetter, however, that had caused the next evening’s performance to be cancelled after one actor went down with hypothermia.

For those who did see Metamorphosis, though, it was possible to check out some of Purcarete’s signature motifs. The white-clad, pasty-faced performers who resemble apocalypse survivors; the pair of anachronistically be-wigged fops who seem to have stepped out of a Restoration romp; the ostentatiously curtained proscenium arch that the performers step out of, revealing the exercise as pure artifice – all reappear in Faust.

If Metamorphosis is water, then Faust is without doubt fire. It’s also brimstone, blood-and-guts, lust, pure primal sex and a bombastic, sense-assaulting carnival of the sacred and the profane that explodes into a post-apocalyptic orgy of excess.

On Sunday morning, sitting at a trestle table in the courtyard of Sibiu’s National Theatre Radu Stanca, Purcarete calmly explains that all this is merely a big box of tricks.

“It isn’t Hell,” he points out. “It is something called the Feast Of The Witches, and these are all tricks which Mephistopheles conjures up to impress Faust. But you can see the strings. Nothing is hidden. It is all just cheap theatrical spectacle.”

Beyond the high-and low-tech jiggery-pokery of which Purcarete has proved himself a master – both in his last Edinburgh visit two decades ago with a version of Alfred Jarry’s Ubu Rex, and in Aeschylus’s Danaides, which visited Tramway in the mid 1990s – one of the most striking things about Faust is its casting. Purcarete originally intended two male actors to play the leads, but one died. His replacement was the young actress Ofelia Popii, whose feminine presence lends an ambiguous, sexually charged edge to the Faust/Mephistopheles relationship.

The last time a woman played the devil in this context was when Elizabeth Hurley was the scarlet woman who tempted Brendan Fraser in the Hollywood remake of Bedazzled. The 1967 original was a swinging London take on Faust that took intelligently absurdist advantage of Peter Cook and Dudley Moore’s upmarket comic partnership.

Mercifully, however, Popii is no coquettishly kittenish Hurley, but instead gives a magnificently unfettered performance that is by turns savage, desperate and, perhaps surprisingly, heartbreakingly vulnerable.

In the flesh, the 30 year-old actress is fresh-faced, porcelain-skinned and healthily gamine. Considering she survived both Faust and the soaking in Metamorphosis on consecutive nights, her appearance at all during daylight hours is remarkable. But then, as one of the National Theatre Radu Stanca’s resident actors, and with Faust her fifth collaboration with Purcarete, one suspects Popii would put herself through anything for the director.

“The most interesting part for me,” Popii muses, “is the way Mephistopheles wishes to understand the divine part of things. He has this illusion of love. He thinks he feels it, but for him it is all about the body. He’s always looking for something he can never find.

“He’s never relaxed, never calm. Mephistopheles isn’t human, because he doesn’t have feelings. For him it’s all fake. That vulnerable side of him comes from a sadness from long ago, and in the end that’s what stops him from being able to love.”

At first glance, then, Faust may look like a horror story, but the cross-gender casting also suggests something else besides. For, despite its scale and the mass of writhing bodies onstage throughout, Purcarete’s Faust is the most intimate of love stories between two very different entities. If Faust’s lifeblood exists all in the mind, then Mephistopheles is ruled by the body. The spiritual enlightenment they both seek – the love, if you will – which ultimately keeps them apart remains unrequited and unconsummated. As death parts the pair, that is the real tragedy of Faust: to be rendered loveless in a loveless world.

It’s midnight in Sibiu by the time Faust finishes. The rain has finally died off as the audience disperse, awed into silence as they take the bus back into town. If they, along with Faust, have learnt anything, they’re perhaps wisely keeping it to themselves. The city centre streets are equally quiet. Save for the odd leftover festival-goer, the cellar bars are deserted. A solitary dog, black as night, pads its way out of a side-street, stops for a moment at some imagined disturbance, then goes on its way.

If any Faustian pacts are to be made, they can wait until morning.

Faust is at Lowland Hall, Ingliston, from August 18-22, 7.30pm; www.eif.co.uk/faust