There's a nagging feeling in my gut, this should have been rather better than it was. The concept, of live-action role-players (LARPers) who accidentally manage to summon a genuine demon, is borderline genius, and the presence of Dinklage, who since filming has become a huge star for what's basically glorified LARPing in Game of Thrones, is undeniably fortunate. But the rest of the cast range from merely okay - Zahn as geeky magician - down to entirely bland and forgettable. Unfortunately, it's the latter which covers Kwanten as broken-hearted male lead Joe, who doesn't want to be prancing round a forest dressed in armour and waving a foam sword, after his girlfriend dumps him. Frankly, I can see why, since he comes over as an irritating and self-absorbed jackass - never mind dragging him along for some fantasy frolics, I'd gnaw a limb off, to avoid spending a full weekend in his company.
I think the main problem is the film's inability to decide whether it wants to be horror or comedy. Well, actually, it wants to be both, but it's always a tricky balance to strike. While usually, one side or the other is favoured, here, the compromise seems to cripple both aspects equally. While there are some laughs to be had from Zahn and Dinklage, there are long periods where humour is abandoned entirely; conversely, it's too long before the horror angle shows up to any significant degree. The effects work is a bit variable, to say the least, and the ending feels as if it was bolted on from an entirely different film altogether. Indeed, it may well have been. This had a lengthy struggle from completion to the screen, with the producer firing the director and apparently recutting things. Hard to say if this is the core of the issue: regardless, the end product is rarely more than lightly entertaining, and has rather more dragging than dragons. You could argue this is nearer to "bad" than "badass", but I guess "Knights of Mediocrity" wouldn't have sold as well.