I’ve watched this movie at least 10-12 years ago. I don’t remember much, but it was a dark fantasy movie, maybe even a bit horror like. If I remember correctly the setting was sort of medieval as well. The protagonist was a male, probably younger than 20, and he was with a group of people around his age. He went somewhere and did something (I don’t remember what) and I think it freed some kind of monster, which then proceeded to kill people. The main point was that the protagonist now had to figure out the real name of that monster and it was the only way to stop it. At the end, I think he found out that the monster is him and he said “You are me” or something like that and that’s how he won.
That’s all I can remember, so I’ll be grateful if anyone knows about it.