Let's get the bad out of the way first, in part because the movie did exactly that. The writing, especially in the first part of the movie, could be pretty bad. Whoever wrote the banter needs a lot more practice at that particular art. That plus some pretty bad acting was almost enough to make me turn the movie off. Luckily, just as I was deciding not to throw good time after bad, they reached the supernatural strip club (brothel? general sin palace? hard to tell) and that idea was itself intriguing enough to keep me watching. From there, with the exception of a bit of hammy acting (and persistently bad acting from the bachelor party guys), things improved a bit, not in the least bit because the opportunities for "banter" grew more infrequent.
But the central conceit -- the Lily figure from V/H/S -- was a good one to choose. It had potential, and provided a complexity to the standard slice-n-dice that most killer films don't have the room to explore. Mind you, this isn't a deep engrossing character study or anything -- we never learn much about the backgrounds of most of the characters (and Mr. Nyx absolutely could use a movie of his very own) -- but the basic premise and the complications provided by the nature of the titular Siren are solid enough to carry the film. The low budget shows (not in the least in the aforementioned poor writing and acting as much as the more visible products of low budgets) but the film is absolutely solid for the budget it does have. Since this is a standard film rather than found footage, the filmmakers couldn't operate on a microbudget but did manage to get their money's worth from the $300k IMDb says they had. I bumped my rating up a solid point in acknowledgement of managing to do so.
As with the V/H/S segment this movie came from, Hannah Fierman does the most with what little personalization is allowed to a character like hers. She certainly commits, and presents a compelling dichotomy between the Beauty and the Beast aspects of her character.