I suggest you take out the supernatural aspect of this movie and just think of it primarily as another cops vs. serial killer story. Yes it's true, the killings are supposedly done by a "dying god", worshipped for thousands of years by some Indian tribes who are themselves becoming a vanishing race. But the "story" about this evil creature, and the visuals of it, are really not what makes this movie interesting.
First of all, it's filmed in Buenos Aires, yet made by a French company, the dialog is in English and the lead actor American. How unusual is THAT?
Sean Fallon (also appeared in Flags of Our Fathers) plays the stereotypical "bad/good" cop. You know: the one who breaks all kinds of laws, has a bad attitude--and yet manages to get the killer better than the good cops. This is a well-worked convention, but I thought Fallon did a really good job with the part and I loved watching him. There is a string of (bloody) murders of prostitutes around the city, an election is coming up, it's politically embarrassing to the mayor (of course) if an end isn't put to this before the election, so Fallon, with a by-the-book rookie assigned as his partner (aren't they ALWAYS?) has got to get a move on and do his thing. So most of the cast are playing cops, prostitutes and sundry other low-lifes, with an Indian or two thrown in. Watch it with low expectations, and I think you may enjoy it, as I did. It's better than your average Indie film.