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)
Vampires don't necessarily live in castles. Count Dracula only did because he was a count.
Also, vampires can see themselves in most mirrors as long as no silver is used as the reflecting surface.
I think this makes sense more than just not having a reflection, if the rest reflects the "Judas was the first vampire" bit, which is at least where some of the silver avoidance is set to come, because of the silver pieces.
Vampire: The Masquerade lore has Caine (as in the biblical Caine and Abel) as the first vampire, and my search for the idea that in some versions Judas is the first vampire mostly turned up results of people saying they were only familiar with it being Caine and expressing confusion about where the idea of Judas came from.