Like most modern vampire and werewolf creations, Hemlock Grove takes a unique spin on existing mythology. I haven't read the book yet, but the Netflix original series speaks to Romanian and Romani origins. The terminology and creature construct for their vampire, however, is Slavic (the strigoi is the Romanian vampire). The Upir can be found throughout Ukraine, Russia, Poland, and other Slavic regions with minor variations in legend and spelling. As an aside, the show's mythology gets more confused when considering the vargulf, which is Norse.
The Upir is probably a combination of the Slavic pagan mythology and superstitions that carried over once the Russian Orthodox Church was established. People who committed grave sins or did not believe in God were excluded from burial on church grounds. It was rumored these people were witches in consort with the devil and possessed prior to death. Bodies buried in unholy ground were also said to decompose slowly.
In keeping with Upir mythology, the vampires on Hemlock Grove can walk in daylight and appear as normal humans. The Upir are born with either a caul or other physical deformity, such as a tail. They feed off the emotions of others, creating chaos and pain for their personal nourishment. The Upir also feed off others. As in: eat them. In Hemlock Grove, a person is born an Upir rather than transformed, and bleeding to death (or perhaps just dying) is the final step in their transformation. This doesn't necessarily conflict with Upir mythology since the Upir raises from the grave. Where the book and the mythology do diverge is the victimology. Most Upir myths involve the consumption of small children before devouring the entire family. Hemlock Grove opted for a more sympathetic version. Kind of.
Despite his malicious tendencies, Roman Godfrey is an interesting character. I find him to be a conflicted soul without the tedious introspection and brooding we see featured so frequently. He's screwed up, angry, and not purely evil. He isn't good either. Far from it. But I suppose that's what makes it interesting. Olivia, played by the gorgeous Famke Janssen, is a fabulous Upir. An ice queen with a shriveled little heart hiding in there somewhere. Many of the characters are odd and broken. I enjoyed season one and feel that the werewolf transformation is amazing. I can't recommend season two after seeing the finale.
Have you seen the series? What did you think of their interpretation of the vampire?