- Ensemble Darkhorse: Ben Foster's character, "The Stranger".
- Faux Action Girl: Amber in the sequel. She exists mainly to complain about how Stella is useless in a fight and is going to get the rest of the group of vampire hunters killed. She kills exactly zero vampires, gets Todd killed when she panics in the middle of their first operation as a group, dies herself during the climax, and provides nothing in the interim except needless antagonism towards the female lead.
- Sequelitis: The first 30 Days is noteworthy for its departure from so many worn-out vampire cliches, even borrowing a few details from zombie stories back before it was fashionable to do so. Dark Days, by contrast, is as paint-by-numbers as you get, replacing tense survival horror with generic guns-blazing action and reintroducing several of those vampire cliches in the forms of Dane, a Friendly Neighborhood Vampire who works with the vampire hunters and feeds on blood packs; and Lilith, an Evil Is Sexy blood-bathing Vampire Monarch (named Lilith) whose design hits much closer to Cute Monster Girl than even other female vampires. She even has a human pet! That doesn't stay human. The kicker to this? The script is co-written by one of the creators to the comics.
- Special Effects Failure: The CGI "blizzard" is Syfy-standard, as is the killing of the head vampire and Eben's death.