Vampires are fictional characters appearing in American comic books published by Marvel Comics. The concept of the Vampire has been depicted by Marvel to varying degrees of significance. Bearing strong resemblance to their literary counterparts, Marvel vampires mostly are an undead subspecies of humans which sustain their immortality and paranormal power by drinking the blood of the living. Unlike most other depictions of the creature, these vampires have their roots in both the supernatural as well as biology. Victims are converted to vampirism via enzymes carried in the vampire's saliva which cause reanimation once introduced into the bloodstream during feedings.