Excerpt drawn from A Study of the Vampire and its History, an essay.

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      The exact date that the vampire emerged into being is unknown. Since the evolutionary process that resulted in their species was originally deemed freak accident, no detailed reports exist that document their rise. That they are, or were, human is certain: it was humanity’s craving for eternal life combined with a small innate sense of the so-called ‘spiritual’ realm which allowed for the species’ evolution. Furthermore, though both shinigami and vampire may mask their presence to normal humans through the manipulation and control of spiritual energies, the act is not natural for the vampire and requires some small degree of effort, indicating that the vampire is fundamentally tied to the mortal realm, and not the spiritual. By contrast, the shinigami is required to expend a similar effort in order to become corporeal and interact with mortals, and thus the conclusion is drawn.
      Further difficulty in determining the vampire’s origins arises when examining their records and lore, for though the vampire can boast one of the most extensively recorded histories known to exist on Earth—second only to the shinigami and perhaps the Hebrews—no two sets of records or journals can agree on a single common ancestor. Rather, the vampire as a species appears to have begun as multiple isolated incidents within the span of around thirty years, with sporadic repeat occurrences every few centuries, followed by a gradual but steady proliferation.
      Also of note is the singular failure of the shinigami in catching and preventing the vampire’s evolution. Certainly the error is due in part to the encasement of the vampire’s soul, which would have prevented any shinigami from sensing the human’s approaching death; but even so, death is the business of the shinigami, so it follows that some sort of advance knowledge of death must have been present. Any speculation on the reason for the oversight is ultimately futile, however. With so many different instances, it is highly unlikely that any more than two or three occurred under similar circumstances. Whatever the case, the first vampires managed to escape the eye of the shinigami for long enough to ensure their continued survival, allowing their bodies to slowly adapt to their newfound attunement.
      Not being true creatures of the spiritual, the first vampires underwent several major physiological changes shortly after turning, as it came to be called—the most prominent being a marked increase in strength, speed, and endurance. In most cases, this change was accompanied by a period of intense physical pain, either in a single excruciating session or as a series of sporadic fits. The few who escaped this side effect were instead subjected to severe psychological torture, invariably rendering them insane madmen or in the worst cases psychotic masterminds. The journal of one such person noted briefly that several of his comrades did not survive the torture; those who suffered physically commonly died from organ failure or internal bleeding, and those who suffered mentally became brain-dead.
      Those who survived the transition, as stated above, became stronger and faster, with noticeably superior reflexes. Early on, these changes only manifested openly as instinct, in circumstances when the vampire might be under mild stress or other cases which require thoughtless reaction, but as the vampire aged the difference became decidedly more pronounced. Vampires as young as a decade can achieve an average running speed of twenty-five miles per hour and can sustain these speeds for nearly twenty minutes. They are also easily able in a single leap to clear horizontal distances of over thirty feet starting from an easy jog, and can generally jump over twice their height from a standing position. All vampires continue to grow stronger as they age, though the rate at which they mature gradually decreases over time, meaning that the difference in strength between vampires of twenty-five and fifty years is more pronounced than is the difference between vampires of seventy-five and one hundred years, though the age difference is the same.
      Other changes to the species were much less beneficial. The vampire almost immediately developed an extraordinary allergic sensitivity to sunlight, for reasons that even now remain unclear. The initial reaction was, in fact, so violent that direct exposure for even a few seconds would cause the vampire’s internal body temperature to literally skyrocket, often resulting in spontaneous immolation. Even indirect exposure was extremely painful—especially, it appears, to the eye and the sinus regions, for if light were streaming into a darkened room the vampire would not be able to even look near the source without their eyes watering.
      Because of this side effect of the evolution, vampires naturally became nocturnal in habit, transitioning to their new lifestyle within a matter of decades. Their still-adapting physiology allowed their night vision to adapt rapidly in individual cases, and the traits were cemented and enhanced into the species by successive generations. The vision of modern vampires rivals and in some cases surpasses that of most predatory felines for distance and clarity, and they are only truly blind in the complete absence of light.
      Interestingly, vampires seem to suffer no ill effects from exposure to moonlight, though it is in essence merely sunlight reflected off the moon’s surface. Cause for the selective photosensitivity could be certain types of direct radiation that is absorbed by the moon’s surface, but very little significant testing has been done to ascertain the truth of this supposition—though it has been consistently observed that light from the full moon seems to have a pronounced euphoric, almost drug-like effect on the vampire.