Having endured a summer of messiah wizards, robot romps and all-American superheroes, and with another long, cold vampiric winter ahead, a new beast from the north has arrived to break up the monotony. This is the autumn of the troll. Smashing through the vampire, werewolf and zombie stranglehold on the multiplexes, Norwegian director André Øvredal brings some of his homeland’s medieval mythology to the big screen with Troll Hunter. It’s The Blair Witch Project meets Cloverfield meets… The Three Billy Goats Gruff.

Breaking out of the icy north with a hilarious trailer and on target to bring in a mean cult following, we caught up with Øvredal, a director on his way to the big time, at this year's Edinburgh International Film Festival, where his film had its UK premiere and thrilled three sold-out audiences. Already the talk of the fest before its first screening, trolls appear to be capturing film-goers' imaginations, just as they captured Øvredal’s. "I grew up with films in the 80s, with Spielberg and so on, and I wanted to make a very Norwegian version of that with a very tough central character. Not an American movie hero, but a much more down-to-earth, very realistic Norwegian guy who has this amazing thing that he needs to do." Sound familiar? With raw talent and an excitable imagination, Øvredal is already tipped for bigger Hollywood productions. But what about the trolls? "I always loved the trolls, and I found that [the people of Norway] had kind of lost touch with them – they're such a big part of our cultural heritage and they're not really utilised in any particular way. So I figured that was a great contrast, to have a guy who is an ordinary worker for the government and what he's doing is actually fighting to make sure that these trolls stay in their reserves."

Using meta-monster found footage – mockumentary style – Øvredal's film shows how a group of student filmmakers find their way into a well-guarded government secret. The suspicious deaths of a number of bears lead them into the murky underworld of troll hunting, where a disgruntled government lackey shows them his overworked, underpaid, extremely hazardous working life. Tasked with keeping massive mythical beasts within their territory, our amateur documentarians uncover more than they bargained for. Pointing out idiosyncrasies and questioning ignorant workers along the way, it's as funny as it is inventive. "I think that the format of mockumentary helps insist on the reality of everything, and then it becomes more absurd," says Øvredal. "It also makes it possible to talk directly about trolls and take them seriously. Everybody's seen documentaries and things from a news segment, it's a language we know – somebody talking very seriously about a topic – and when the topic is obviously not serious, it can become funnier."

Working with a low budget also kept the creative juices flowing. Øvredal's clear Spielberg influences appear to have been held at bay, affording him the kind of creativity a break-out debut needs. "We can't do Jurassic Park in Norway – it's going to be too expensive – so that was a way of hiding the trolls when we needed to. Also, that required me again to build lots of suspense and use other entertaining values, rather than actually showing the trolls on screen all the time." Shooting in mock-documentary style also allows Øvredal to invent much of his own lore to keep the troll stories interesting and fresh – do power lines really double up as troll electric fence perimeters?

Expectations for this debut are high and there's already an American remake in the works, so how long will we have to survive the trolls? "Having the Troll Survival Guide [a pamphlet handed out at each screening], I guess I could do it forever!" We'll have to wait and find out if the box office says the same.

Troll Hunter is released in UK cinemas on Friday 9 September. You can hear my review on the BBC Movie Café on Thursday 8.