In the fictional world of the television series Buffy the Vampire Slayer and its spin-off series Angel, a vampire is a unique variety of demon that can only exist on the earthly plane by inhabiting and animating a human corpse. In Fray, a Buffy comic book spin-off set about a century in the future, vampires are also called lurks.
The vampires in the canonical Buffyverse differ greatly from those that appear in the 1992 Buffy the Vampire Slayer movie. The movie's vampires are able to fly, look pale but relatively human, and do not crumble to dust when killed. The canonical vampires, introduced in the first episode of the television series, are demonic spirits that inhabit human corpses. Because of their partly human nature, vampires are considered impure by other demons who sometimes call them "blood rats".
According to Rupert Giles, when the ancient race of demons called the Old Ones were banished from Earth, the last one fed on a human and mixed their blood, creating the first vampire. According to Illyria, vampires existed during her time as an Old One—long before the rest were banished from the realm. Vampires possess all the memories and skills of their human predecessors. They also retain much of their host's personality, including any mental illnesses or emotional instabilities. For example, Spike (unlike most vampires) retained his love for his dying mother and Harmony kept her vain, shallow valley girl personality and her love of unicorns. Darla tells the newly turned Liam/Angelus that "what we were informs what we become"; after her resurrection as a human she says that the darkness he unleashed as Angelus was always in him as a human, long before they met.