Okay, just kidding. I just wanted to lower your expectations so anything I write will seem better by comparison. Yes, I am talking about vampires here, but the pre-Twilight, pre-Anne Rice, even pre-Dracula kind.
I apologize for this being a long post, I've tried to condense it. I've also put no essential bits within the spoiler tag in order to give readers the opportunity to get to the heart if the suggestion with as little reading as possible. If interested you can open the spoilers for a little more info.
The history behind the idea.
What I am not suggesting.
Choosing at the beginning of the game to be a vampire or not. Nor am I suggesting vampire npcs, or a type of spawnable creature. I'm not suggesting new weapons, items or inspirations, although I wouldn't be opposed to them.
What I am suggesting is that on a very low probability when a person is dealt the killing blow, they would be given the chance to come back as a vampire. (Maybe a contract would pop up from satan asking you to either die or sign away your soul and come back as a vampire.
Some technical details, nothing important.
What being a vampire might entail.
Gain the witchcraft ability to spread disease (maybe some sort of ongoing debuff to a character's stats, or a decrease of what you can gain in gluttony. Nothing crazy, but enough to be annoying.) And the witchcraft ability to disease plants or, in time as they are implemented, farm animals (they take longer to grow and produce less when they are finished growing). Each person/crop/animal affected in such way would have an "aura of disease" which would mostly serve to remind people there is an active vampire out there. This aura and the defuffs it entails would not go away until the vampire is killed.
The vampire could kill and be killed without leaving a killer's scent. NPCs wouldn't do business with them in Boston. Obviously few people would trust someone who came back as a vampire and any community that choose to protect one would be putting itself in great danger from neighboring communities.
Besides the witchcraft and the killers scent the major difference would be graphical, they look like someone who had been killed. No fangs, capes, and for the love of everything holy, no sparkles. They just look dead, that's all. They don't have to avoid wild garlic or drink blood to survive. None of that kind of stuff. Basically, if they choose, a person could be reborn a vampire and go on to live a relatively normal in game life.
What the game has to gain from such a mechanic.
I think first off it would disencentivize killing ever so slightly, I don't think it would discourage it too much, but maybe enough to think twice about dealing that killing blow if that person might come back and curse his crops and entire community. Also some communities might get to thinking that guy who runs around killing people for the hell of it and accidentally creating vampires might be just as much of a problem as raiders or even the vampires themselves.
Also I think it will take a little bit of the edge off being killed in the game, especially for players who've sunk a considerable time into their characters (especially if the probability to be spawned as a vampire increased slightly based on game-play or stats.)
Also in general I think it would be a pretty interesting dynamic to have people and crops being diseased and the community having to gather together to hunt for a vampire or employing someone to do it for them. I also enjoy the idea of the lone hermit vampire who never cursed anyone trying to eek out a lonely existence in the woods living in fear of the day he was going to be killed by a mob trying to find the vampire that cursed their community. It fits quite well with the idea I have of Salem Online.
Okay so that's my idea. Tear it apart.
A problem and possible solution.
A few small ideas.