As always, it's a pleasure to see a film industry other than Hollywood do something so accessible, and the barmy, free-wheeling story makes the concept behind Rare Exports all the more fun.

It's Christmas Eve and the enigmatic overseer of an archaeological dig on a Finnish mountaintop has unearthed something unspeakable in the mountain below. It's a set-up that could have been just another monster-awakened-from-aeons-of-sleep horror movies, but this monster is a bit different.

Borrowing more from age-old northern Scandinavian myths about Santa Claus rather than the westernised shopping centre figure, the real Santa Claus is a monstrous entity that doesn't care about who's been naughty and nice. He and his army of helpers are monsters who live on raw flesh, which explains why all the children are going missing.

Down the hill, young Pietari (Onni Tommila) lives with his reindeer hunter father Dad, and the takings this year aren't good, threatening the livelihood of the local industry. When they find what looks like every reindeer in the region lying dead and butchered in a snowy field, it leads Pietari, his Dad and their friends and co-workers up the mountain to see if the strange activity they've seen up there is related.

The movie doesn't make a particular secret about the fact Santa's the monster they ultimately find and in a hilarious plot device, his minions are the wiry old men with long white beards (but pirecingly evil eyes) who usually represent commercial Santas around the world – except they dart here and there in the dark forest, closing in to attack like wolves or zombies.

Pietari's dad Rauno (Jorma Tommila) smells opportunity. If they can dig up the real Santa Claus – a gigantic horned beast about ten stories high, frozen in a block of ice – they'll be in the money for life.

But to do so is to invite the ire of the loyal, mute helpers, and the fight is on in the snowy wastes to grab a payday and stay alive in the process. After the tension and clever mix of horror and laughs of the set-up, it devolves into a bit too much of a CGI action film during the climax.

Another problem that takes marks off is that despite a great setup and an imaginative story, Rare Exports badly mishandles the 'see the monster' issue. In films from Jaws and An American Werewolf in London to Godzilla , directors understand the secret sauce is in how much – and when – to show of the monster.

After teasing us with glimpses of the enormous beast, huge curved horns jutting from the ice, the fight is instead with the helpers, Santa Claus him/itself never making an actual appearance.

But despite those stumbles it's a good fun horror romp, working because it takes itself seriously, the script and characters never devolving to camp in order to wink at the audience about how silly the whole thing is.