[victorian vampires thing] (needs setting name)

[Kappa]

This world, which is desperately in need of a name or at least a better working title, is approximately similar to Earth but not directly based on it in cultural or geographic terms. They have a country that is broadly similar in culture and technology level to Victorian England, and a magic system that includes vampires.

The way vampires happen is this:

Every living thing has a lifeforce, an insubstantial magical energy field contained within their body. Conscious self-aware beings can learn to use their lifeforce to work magic, by separating out parts of it and shaping them into spells; everything else just sort of has it.

When a living thing dies, the lifeforce also dies, and then dissipates shortly afterward.

It's possible to mix living and dead lifeforce, such as by draining someone else's lifeforce into your own (which kills them if you take all of it, and it's very hard to stop at just a fraction). If you do that, your lifeforce will 'digest' the foreign life before it can dissipate. But if you do it often enough and in significant enough quantities that in the long term you can't digest it as fast as you acquire it, and thereby accumulate enough dead lifeforce to outweigh your own living essence, you become a vampire. A vampire's lifeforce is dead, but still capable of sustaining itself indefinitely by feeding on the living.

Vampires start out on the edge of starvation, ravenously hungry for more living energy. At the beginning, consuming one person's lifeforce will hold off their dissipation for a few days. But every life they add to their own makes subsequent meals last longer. Eventually, after a few hundred kills, a vampire could go months between meals without suffering more than moderate discomfort.

Vampires can work magic more or less the same way living people can, but a living person's lifeforce grows with use, becoming stronger and more vital the more they work magic with it. A vampire's "life"force grows only when they feed another life to it.

Besides the magic that anyone can use, vampires have two specifically vampiric powers: shapeshifting, and feeding. They feed by drinking blood, and using the blood as a conduit through which to reach the lifeforce in the body. This means that blood separated from a body is completely useless to them. It is possible to feed only partially, leaving the victim alive, but most vampires never bother to learn the skill because if you don't fully add someone's life to your own then you get no increase in power and no increase in the length of time your next meal will last you.

They can shapeshift into almost any conceivable form, but it takes time and practice to master the power, and many a vampire has starved to death after turning into mist and failing to figure out how to turn back in time. (However, if you know the trick, it's possible to eat while in mist form: you just have to get someone to breathe you, and then you'll have the same connection you would if you drank their blood. With the added benefit that if you fit your entire mist form into someone's lungs, and they fall unconscious, you can pilot their body as though possessing it.)

In addition to its straightforward applications, vampiric shapeshifting also grants them supernatural speed, strength, and grace. On top of that, they usually have enhanced senses as well, although those are somewhat more dependent on the skill of the individual vampire.

If a vampire feeds from a pregnant woman, they can consume the lifeforce of the fetus completely without draining the mother, which results in a quick and usually fairly harmless miscarriage. This counts as taking a full life for all purposes that distinguish between full and partial feeding.

The most efficiently power-augmenting frequency for a vampire to feed, once they've taken enough lives to survive that long between meals, is about once a month. Any faster than that, and the added value of the extra lives drops off sharply.

If a vampire feeds from a lifeforce too much unlike their own - particularly across the sapient/nonsapient barrier, but also between sapient species with very different psychology or body plans - the alien lifeforce disrupts their shapeshifting, and they begin changing shape somewhat at random, often asymmetrically and in ways that draw only a distant inspiration from any real creature. Vampires with this problem are sometimes called 'goblins' or 'demons' or 'horrors'. If they stop eating things that aren't good for them, they will eventually recover, although they might always have a little bit of lingering trouble controlling their form. If they keep eating things that aren't good for them, the problem will get worse and worse until they're shifting so uncontrollably they can no longer maintain a mouth long enough to eat someone with it, and then they will starve. (Feeding via mistform requires a much more delicate touch with the shapeshifting than someone with this condition can manage.)

Magic users are especially delicious to vampires - the more powerful, the better - because their lifeforce, being unnaturally developed by the practice of magic, is proportionally more nourishing than an ordinary person's.

The setting is a masquerade setting: most people don't know magic exists. This is because, as the local Industrial Revolution picks up steam and scientific inquiry into the natural world becomes an established discipline, magic users are universally very reluctant to step up and admit they can do magic so someone can investigate it. And the ones that do are often eaten by vampires before they can get anywhere, because that's generally what happens when you openly and publicly admit to doing magic.

One final secret, as yet undiscovered by anyone within the setting: It's possible for a vampire to turn... not back into a living thing exactly, but into another sort of creature whose lifeforce is once again capable of sustaining itself and growing without cannibalizing the lives of others. The process is somewhat similar to turning into a vampire in the first place: all you have to do is overwhelm the proportion of dead lifeforce within yourself by consuming a single life, all in one go, whose lifeforce is significantly greater than your accumulated vampiric power. Of course, this means winning a fight with a magic user who is by necessity much more powerful than you, and is probably also hundreds of years old or they wouldn't have had time to get that way, and has been successfully evading death by vampire all that time. That rather daunting collection of obstacles would be why no one's figured it out yet.