In the Netherlands, the main December holiday celebration isn't Christmas, but Saint Nicholas' Eve and Saint Nicholas' Day on December 5 and 6, the name day of the historical Saint Nicholas, who is represented in Dutch culture as Sinterklaas (a figure similar to the North American Santa Claus). Like Santa Claus, Sinterklaas brings presents for good children, coming down the chimney to deliver them. He's aided by the somewhat problematic helper known as Black Peter, typically represented by white people in blackface, which has created a bit of controversy in recent years (the character started out representing a Moorish servant, but these days he's more commonly described as being blackened with soot from climbing down chimneys). Dutch filmmaker Dick Maas' horror movie Sint (marketed in English as either Saint or Saint Nick) takes all of this knowledge for granted, which makes sense for his native audience but provides a bit of a steep learning curve for foreign viewers (I got my basic info from Wikipedia, of course).
Plus, the concept of the movie is that everything people take for granted about Sinterklaas is wrong; the historical Saint Nicholas is a sham, and the real Nicholas was a rogue bishop who burned villages and murdered children. A prologue shows Nicholas and his band of marauders terrorizing a village in the 15th century, defeated when the villagers fight back and burn Nicholas' ship with him and his followers in it. But his spirit returns every time December 5 coincides with a full moon, and a second prologue set in 1968 shows the undead Sinterklaas, with his traditional golden staff and white horse, slaughtering a family and leaving the young son as the only survivor. By the time we finally get to present-day Amsterdam, there's a lot of build-up for what turns out to mostly be a mundane horror story about horny teens fending off evil.
The real main character is Frank (Egbert-Jan Weeber), a teenage doofus who's just been dumped by one hot girl after cheating on her with her best friend. He discovers the secret of Sinterklaas after his ex-girlfriend becomes one of the demon's first victims, and he's then arrested after he's found at the scene of another Sinterklaas massacre dressed up in a Sinterklaas costume on his way to a party. Frank isn't much of a protagonist, and he mainly just stumbles into the main action by virtue of being in the right/wrong place at the right/wrong time. He eventually teams up with police detective Goert Hoekstra (Bert Luppes), who survived the 1968 Sinterklaas attack as a young boy and has been obsessed with stopping Sinterklaas ever since. Goert's a typical horror-movie obsessive, complete with the crazy wall of newspaper clippings, but his big plan is pretty unremarkable, mainly involving lots of explosives.
Sinterklaas himself isn't particularly scary, although he does have a cool look with his red outfit, his giant staff (which he of course uses to stab people) and his massive horse (plus his Black Peter minions, who are definitely black from being horrifically burned). He doesn't speak, and his motives (other than wanting to kill lots of people) are not very well-defined. At one point someone remarks that Sinterklaas will only kill the naughty, but that's quickly corrected, and he doesn't seem to have any particular standard about whom he kills. There's a half-hearted subplot about a government conspiracy to cover up the existence of the evil Sinterklaas, but that's poorly developed and doesn't really fit into the main story. Some of the kills are entertainingly gruesome, and there are a few amusing bits of black humor. But the characters are dull and the plot never goes anywhere exciting after the two prologues. Goert's big plan doesn't amount to anything, and the movie ends with a lack of resolution that's meant to be unsettling but just makes the whole preceding story feel like a waste of time.