So this is based on some plurk plotting and subject to tweaking depending on what others want to do! but yes hello.
Anne would be the queen of the country, seemingly human and visiting this town due to the increased attacks. In reality, she is a pureblood and it's a total state secret that the royalty is largely controlled by pureblood vampires. She probably (?) visits the town often more quietly due to her prey Aramis being there.
Lancelot is human and Merlin's willing prey, initially the only one who knows about his status as a vampire. Open to other specifics here, I don't have much planned out so far for him.
Emma is human and a hunter, older sibling to Stiles for the purposes of the AU. Their mother is Snow, and as noted above she got turned into a vampire and they would be separated? The two of them could be looking for her not knowing she's a vampire yet.
Art was turned into a vampire at 16 and it's been his secret for five years as he works as a vampire hunter/posing as human. He's actually looking for a human scientist who was basically the one behind Art's turning. He'll likely get involved in the matter of Elsa as the mayor, on her side basically to help keep the secret re: Bucky.
Yona planned to be a royal pureblood from a neighboring country fantasy vampire Korea? and currently escaped to this town since she's on the run from her castle. Since she's alone in this scenario, I'm open to both people who would help her or run-ins with hunters. She doesn't have prey and Jae-ha was supposed to be hers (sent from one of the four villages in her country!1 when she was a princess to make sure she always had "e"), so they'll be meeting during the event as well.
Robin doesn't have much planned so far, but she'll definitely be human and possibly a researcher helping with the situation to try to figure out a solution.