Vampires are undead beings whom originally humans infected/resurrected by supernatural pathogen that bestowed them heightened sense, supernatural strength, speed, agility, and ability to transform into huge bat-like creature, all of them at the costs of bloodlust where they must feed on human blood to keep that thirst from corrupt their minds.
Origins of these undead beings are proposed as result of failed experiments of Dark Arts in Transylvania for the way to revive the dead with both magic and use of blood taken from vampire bats. Though deceased test subject succesfully revive, the test subject turned into a diseased bloodthirsty undead creature who killed random humans before being destroyed himself. However, the test subject's saliva revealed to carry supernatural pathogen that also indirectly created through the experiment which causes anyone whom he bite died and rises as another undead beings that later become first vampires whom spread their vampirism like disease up until the antidote for vampirism uncovered and contain it from becoming pandemic. Prior to the discovery of the cure, vampire's existence inspires the folklore and legends about them.
Contrary to the folklore and legends about them, vampires are products of infection by supernatural pathogen that can be treated like regular disease with medications, and thus not affected by religious symbols (such as crucifixes and holy water) and able to walk on consecrated ground (ex. churches or temples), . The belief where they can turned into mist, can only enter someone's house if invited, inability to cross running water, inability to cast shadow, and lack of reflection are false and exaggeration from the truth about them.