Vampires are a supernatural species in The Vampire Diaries franchise.
Physical and Emotional Characteristics
Vampires look like normal human beings for the most part. However they do have a cooler body temperature compared to humans, which can be disguised drinking caffeine. They undergo a facial transformation when they feed, smell blood, or experience particularly strong emotions. This transformation includes a paler complexion, blood rushing to their eyes with small veins protruding around the area, and fangs appearing on their canine teeth.
Another characteristic of vampirism is enhanced emotions; whatever a person was feeling before the Change is amplified and can be hard to control.
Vampires need to drink blood in order to survive. While any animal blood will sustain them, it is human blood that gives them stronger powers. Consuming alcohol can help a vampire with keeping the bloodlust under control, presumably dampening it for a while.
Damon eats human food during a trailer for Bloodlines, and Stefan is in a dinner situation with Elena and Bonnie in which it is likely that he eats, and he also cooks for Elena and claims to love garlic. Vampires can also ingest alcoholic drinks for pleasure with no side effects, and Lexi also states that alcoholic beverages help to stop or surprises the need to feed so much
If vampires are unable to feed on blood, they eventually weaken to the point that they are unable to move or speak. Skin begins to dessicate after about a week, and then they mummify, becoming a living corpse rather than actually dying.
Vampire powers are made stronger by consuming human blood. If a vampire does not drink human blood, these powers become weaker, and are prone to being less effective and unpredictable, or not working at all. Age also plays a factor in how strong a vampire is. The older they are, the more powerful.
They can heal exceptionally fast. After Stefan's hand is accidentally sliced open by Jeremy Gilbert, it heals over in a matter of seconds. The same also happens to a stab wound inflicted on him by Damon. However, there is a slight inconsistency with healing between episodes. Stefan's hand heals and leaves no trace of blood, suggesting that it must have been reabsorbed. There are certainly no smear marks that would suggest wiping it off, and the amount of blood that was dripping from his hand and around his fingers could only really be washed away with water. Yet there is a clear trail of blood on his flesh after his stab wound has healed in the next episode, though it may simply be that there was not time for the blood to have been reabsorbed before the scene ended.
Caroline sees Damon's form manifest itself in the mirror in her bedroom, and in front of her in the deserted corridor of the school. He is locked up in the boarding house basement at the time, so this is either a physical manifestation of his body in her mind, or he is projecting himself there.
Damon is shown to be able to control a crow, using it to unsettle both Elena and Stefan as well as possibly spying on people.
The fact that Damon knows that Elena dreamed of him suggests the possibility that he may have been the one to manipulate that particular dream. Stefan has a nightmare about Damon attacking Elena. Upon waking, Damon asks him if he had had a bad dream and admits that he was in Stefan's head.
They have extremely fast reflexes. Stefan is able to catch a football aimed at the back of his head, while Damon makes a show of catching a glass that is fumbled when passed to Elena Gilbert.
There is a suggestion of flight or floating. The vampire (likely Damon) at the beginning of the pilot seems to pluck Brooke Fenton up into the air and Stefan appears to float for the last few feet after jumping from the roof of the boarding house, and seems to fly across the room when he attacks Damon.
The vampires are almost immortal. A vampire stops aging once turned, as evidenced from Stefan, Damon and Lexi--Lexi herself was over 350 years old at her death, but looked like a teenager. Upon their transformation they become immune from all illness and disease. The only way to kill a vampire is by sunlight, set on fire, a wooden stake through the heart, decapatation, or heart removal.
They can jump to and from large heights. Stefan Salvatore jumps from the roof of the boarding house, and later on up to the roof of a store to save Vicki Donovan.
They can influence people's memories with their minds. Stefan manipulates Mrs. Clark, the secretary at Mystic Falls High School, to make sure she enrolls him despite his lack of proper records and paperwork, while Damon Salvatore influences Caroline Forbes to do things she really does not want to on several occasions. Using this power seems to cause the vampire's pupils to contract quite dramatically.
Reaction to pain
They have a higher pain tolerance than normal humans. After Tyler Lockwood tackles him on the football field, Stefan's finger is broken. He is able to reset it with barely a wince. Damon seems to have no reaction (apart from being annoyed) to being stabbed with a paper knife after Stefan flings it at him. Stefan, however, seems visibly pained when Damon stabs him with the same knife. This would suggest that a vampire's resistance to pain is dependent upon its diet.
They have extremely sensitive hearing and can hear conversations a normal human cannot.
They can move very quickly, much faster than a human can. Stefan is able to cross the corridor to Vicki Donovan's room in the hospital at great speed, and makes it up to the rooftop of a store in the blink of an eye. He displays this ability again when he speeds across his room to pick up a paper knife to throw at Damon.
Vampires are much stronger than human beings. Damon flings Stefan quite forcefully into a building without straining himself, while Stefan is able to knock the wind out of Tyler Lockwood after throwing a football back at him from a distance.
Damon has the ability to control fog, using it on several occasions. Katherine also seemed to be able to control fog in children of the dammed.
Vampires can be harmed by sunlight. The only way they can go out in it is by wearing special jewelery such as necklaces and rings containing lapis lazuli. Even a tiny amount of unprotected exposure causes a vampire's skin to burn and blister. These talismans seem to be quite rare, with only Damon Salvatore, Stefan Salvatore and Katherine Pierce being able to go out in sunlight. Lexi mentioned half-seriously, half-joking about wanting to trade rings with Stefan and he remarks "It doesn't work that way and you know it."
A vampire has to be invited into a house before they can enter it, and only by someone who lives there. Caroline inviting Damon into Elena's house did allow Damon to enter, and he could only enter once Elena had given him permission. It also seems to be that once the vampire is invited, there is no way to rescind the invitation. Damon is certain that once he had been invited, he would have no problems going back to Elena's house whenever he desired to do so.
Logan Fell reveals that he is unable to get back into his own apartment after his becoming a vampire, even though he lived alone. This makes for some interesting mythology, as it suggests that vampires need invitations into houses, even if no one lives there.
Vervain is a plant that can help people resist having their minds compelled by vampires. It also has an adverse effect on vampires, working like a poison to severely weaken them if they ingest it. Injecting vervain into a vampire's body seems to have an instantaneous effect, rendering them very weak. Damon Salvatore supposedly made sure to wipe out the existence of vervain in Mystic Falls back in 1865 but, unbeknownst to him, the Salvatore family had been secretly growing a supply of the plant through the generations. Zach Salvatore has been drinking vervain in his coffee daily for sixteen years, making him immune to mind manipulation, and making his blood poisonous to vampires.
Stefan and Damon are both seen to have reflections in mirrors. Damon is seen in the bathroom mirror of the Mystic Grill when he attacks Vicki, Stefan sees his own reflection while making out with Elena, and later on in the same episode we see Damon admiring himself in front of a mirror as he readies himself for the party. They are also able to be photograph as Stefan possesses a photograph taken in 1864 of Katherine.
Stefan does not seem to be at all bothered by his clothing reeking of garlic after Jason Harris crams his drawers full of the stuff. He also has no problems when Elena is chopping it next to him for use with garlic bread, and he claims to love eating it.
Jason Harris places a crucifix in a position that Stefan cannot possibly miss yet it seems to not have any effect on Stefan at all. Stefan tells Elena that holy water is decorative.
Jason Harris douses Stefan's bed with holy water yet it seems to not have any effect on Stefan at all. Stefan tells Elena that holy water is drinkable.
Killing a Vampire
While no vampires have been killed by sunlight so far, it has been revealed that sunlight is lethal to vampires, with Damon getting a nasty burn on his face from only a second of exposure to rays of sunlight.
A wooden stake through the heart will kill a vampire pretty instantaneously, causing the body to turn gray and veiny.
As co-creator Kevin Williamson explained in an interview We're going with old legends there -- the reason wood is toxic to a vampire is because it's a dead element. So the idea is when a vampire gets staked in the heart, the toxic wood spreads like a poison through their body. That's why the effect is designed that way.
As shown in Rose, Trevor is killed by having his head cut off.
Removing the heart of a vampire will also kill them.
Vampires can have sex. While there had previously been implications that Damon Salvatore and Caroline Forbes, and Stefan Salvatore and Katherine Pierce had been having sex, it was not explicitly stated if that was the case one way or another. While having a conversation with Stefan about his relationship with Elena Gilbert, Lexi mentions that vampires are able to engage in sexual intercourse.
Becoming a Vampire
A human has to feed on the blood of a vampire and die while the vampire's blood in still within his or her system. It takes approximately 24 hours to for vampire blood to leave a human being's system. The human being is then "turning" where he or she is still not a vampire although has died but appears alive. Also during the "turning" phase, a person is in great pain from sunlight as well as in their jaw and gums (presumably the canines lengthening to fangs) and in their muscles (presumably from the rapid increase of muscle strength). The "turning" phase is not long and a person must decide whether to feed on the blood of human. If the person does not feed, he or she will die but if he or she does feed on blood before that happens, he or she becomes a vampire. No other blood but that from living human being will turn that person into a vampire.
As Damon says, "It's a whole ordeal."