One thing I've always loved about vampire stories is that there are no hard rules. Vampires can be whatever the author wants them to be as long as they're internally consistent within the story. This makes them extremely versatile monsters that can be constantly re-invented and none of them are "wrong".
For example, sometimes all it takes to turn into a vampire is to be bitten by one. And sometimes you have to drink the vampire's blood to turn. Or, sometimes a vampire can just drain your energy without transferring any blood at all.
Of course, the rules can also get a bit ridiculous. Maybe the vampire is required to obsessively count grains of rice first. Or maybe they're required to hop around with their arms out (the chinese Jiangshi). Maybe they can turn into a wolf, a bat, or... fog.
So what's the most ridiculous rule or type of vampire you've come across?
(For the image on this post I wanted the most ridiculous picture of a Jiangshi I could find. I went with a shot from Robo Vampire which has a really fun RiffTrax. The only other Jiangshi I'm aware of is in the NES game Phantom Fighter... because I've never watched any of the Mr. Vampire movies)
I mean, if we're going to avoid the sparkling fucking vampires, then it's gotta be mirrors. Makes no sense within the mythologies surrounding vampires imo.
Running water is about the purifying nature of it supposedly, as other "evil" entities are also unable to.
Wooden stakes being needed to pin them down or be a death blow, there's links between wood and life that make sense within that framework. It wasn't originally just any wood, it was (iirc) dogwood and ironwood. Something like that.
Garlic, also a purifier.
You gotta realize, most of the early written vampire stories did come from existing legends, and those legends did usually have an internal consistency to some degree or another. But not mirrors. Stoker pulled that out of his ass due to not understanding his sources, so it doesn't really match with much.
The idea is that vampires lack souls, and thus fear mirrors, depending on what set of myths you're working in. But there's also supposedly a tie back to real people with rabies being easily startled, with mirrors apparently being something that would do so even easier, but I'm not sure it holds up to scrutiny since the tie to rabies is weak as fuck to begin with, and there's no record of that being a specific thing. It seems more like a hypothesis being projected rather than something with provenance.
But we got being invisible in mirrors.
Now, some people have decided that the mirror thing is because of the silver in mirrors, and add silver being potent against vampires in some cases, but neither is based in any of the known vampire mythology as it existed pre-stoker. And there's arguments there that kinda make sense if you buy into some of the supposed mystical and magical properties of silver. It's tie to the moon in some beliefs would maybe give it sovereignty over most creatures of the night, and is supposedly why it's werewolf killing.
I can't even remember exactly when silver started being common against vampires in books. I know that the Blade trilogy made it seep into pop culture, but it did exist before that.
Most of the stuff around the older books does make a kind of sense, but not that one
Mirrors used to and sometimes still are made with silver nitrite, silver is a purifying metal