One of the great things about vampires is that because they are so mysterious, people have taken many liberties within the confines of the legends. There are a lot of different interpretations of what vampires can be, ways to destroy them, and things that they require.
Some legends say that vampires turn into bats, others can shift into other shapes and creatures. Some can blend into shadows. The essential concept here is to help vampires both avoid detection and hunt their prey effectively. They need to be stealthy enough creep up on people and to stay hidden when necessary. And, make no mistake, these attributes are often added to instill fear in the audience. When any shadow can be a threat, it heightens the danger. And many people already have an innate fear of bats—combine that with their nocturnal nature and they were an easy choice.
Sunlight is another restriction. In some instances, it is detrimental to vampires. It ranges in damage; sometimes it is simply blinding, other times it burns or restricts their preternatural talents, occasionallyit will destroy them. In other legends, they hunt at night because it is easier to avoid detection—not because they would be hurt by the light. It also helps enforce their nefarious reputation. Light represents the side of righteousness and good, darkness has a more sinister and evil connotation. There are a few popular vampires that have no difficulty with the sun at all—and those tend to be the more sympathetic characters. This signifies to me that perhaps this restriction is based more on a literary device than an actual need; it could also be tied back to bats, who sleep during the day.
Holy water and religious icons tend to be a big problem for many different types of vampires. Here again, you have more of a classic good vs. evil situation. I believe the origins of this myth were more along the lines of establishing that vampires are the antagonist. Water is both a symbol of and necessity to life, and as such could be a natural weapon against something that is undead or unnatural. If you believe that religion=good, then it is fair to assume that anything holy (like holy water or a crucifix) would be harmful to anything bad. Others simply believe that if you throw holy water on a vampire, all you accomplish is getting him or her wet.
Since these creatures, left to their own devices, would never die, there had to be some way to kill them. Most tales acknowledge that a stake through the heart is part of that plan. I am not really clear on why it often has to be a wooden stake. In theory, the vampire drinks a victim’s blood to replace their own, and that’s how they live forever. I would imagine this means that they don’t have any sort of functional digestive system—because realistically, this is not how anatomy works—so a stake to the gut isn’t going to help. It would also be incredibly difficult to put a stake through someone’s skull, so that option was out as well (although I should acknowledge here that some legends also promote decapitation as a way to rid yourself of vampires). But the heart is the center of the circulatory system, and it ties back to the blood theme nicely. So a stake through the heart seems like the perfect demise.
There are many other interesting quirks and conflicts for vampires; I will probably revisit this topic another time. Until then, leave me your favorite aspects of myths and I’ll be sure to add it to the next one!