In literature, film and TV, the vampire has varied in appearance and abilities, although a few key traits remain the same. The vampire must consume human blood to survive, their power is at its peak during the night and a human must consume the blood of a vampire to become one themselves. The Vampire Diaries features some of the time-honored traditions of vampire lore but the show also introduces its own elements to the bloodthirsty fiends.
To Become a Vampire, a Human Must Come Into Contact With Vampire Blood
The rule that vampire blood is necessary to kick-start the transformation from human to bloodsucker has existed for generations of vampire stories, and The Vampire Diaries is no different. To become a vampire, a human must die with a vampire's blood in their system. The matter of the human's death itself is irrelevant -- although the body does have to be somewhat intact. However, humans hoping to become a creature of the night must either consume vampire blood orally or through injection, or have a vampire's blood poured on an open wound.
A Transitioning Vampire Must Drink Human Blood or They Will Die.
The Vampire Diaries establishes early on that in order to complete the transformation from human to vampire, a newly created vampire must consume human blood. Animal blood is not sufficient to sustain the transformation, so new vampires who want to adhere to a strict diet of animal blood are out of luck -- at least initially. A human need not die in the process, and vampires can utilize unconventional methods to obtain the needed blood, like stealing blood donor bags or feeding from a recently deceased human. Regardless, a newly created vampire only has 24 hours to have their first taste of human blood or they will die permanently.
Vampires Are All Connected Through Their Blood
In the The Vampire Diaries universe, all vampires descend from the six Original vampires known as the Mikaelson Family -- Mikael, Finn, Elijah, Kol, Rebekah and Klaus. After the Originals were created in 1001 AD, they fed on human blood and thus created the first bloodlines, through which all vampires are connected. The magical properties of the Originals' blood is passed down through each vampire they sire and the ones their progeny sire, meaning that vampires are all one big family. Unfortunately, due to every vampire's link to the Mikaelsons, if one of the Originals die, their entire bloodline follows suit in less than a hour.
The Originals Were Created by Dark Magic
The Original vampires, the Mikaelson clan, weren't created with the blood of a vampire, but by dark magic. After her youngest son, Henrik, is killed by a recently turned werewolf, the Mikaelson matriarch, Esther, used dark magic to ensure the eternal protection of her five surviving children by making them stronger than the werewolves could ever be. Using the sun for life, a magical white oak tree for immortality and the blood of a doppelganger, the Mikaelsons were reborn as the first vampires. Unfortunately the gifts that brought them eternal life also became their greatest weaknesses. They could be harmed and killed by sunlight, and a white oak tree can dampen their powers and put them in a magically induced coma.
Vampires Can Eat Human Food -- and Produce Waste
In a deviation from established vampire mythology, the vampires of The Vampire Diaries can eat food -- from which they produce waste. As long as vampires have a steady stream of human blood in their system, their bodies function like a human's does, although any food they eat won't sustain life, and the vampire will eventually need to consume human or animal blood. Throughout the series, we see vampires eating food. Not only does this keep up the appearance of being human, but it also helps them manage their eternal bloodlust.
Vampires can 'Switch Off' Their Humanity
Unlike vampires in many other stories, the vampires in The Vampire Diaries have human emotions like love and guilt, but they can also switch them off in order to cope with the realities of their misdeeds and to live carefree lives. Doing so usually means the vampire becomes more predatory and bloodthirsty, as is the case with Stefan. While it tends to have dangerous results, this ability can help vampires deal with extreme situations where emotions could hinder their survival.