The term “vampire” is a generic classification of creature, often supernatural, typically characterized by a desire to consume blood, fangs or other teeth designed to that end, and some degree of sensitivity to sunlight. Other characteristics are common, but not necessarily present in all types of vampire. These include predatory characteristics such as increased strength, superior vision and night vision, enhanced olfactory sensitivity, claws (retractile or otherwise), and various vulnerabilities to certain substances or conditions.
Vampires vary widely in powers and abilities, usually based on their origins. Broadly speaking, vampires can be classified by three major origin types: Scientific, Magical, and Spiritual
Vampires with their origins in science are usually living (or quasi-living) entities whose life processes require blood. They may be a subspecies of human being, or altered from the norm through a variety of means. Some biological vampires are quite capable of carrying out normal lives, aside from their need to feed on blood, and may reproduce like human beings. Others, especially humans altered by biowarfare agents, may be infectious and mentally impaired, becoming quasi-feral and aggressive. This latter type can easily lead to a “zombie apocalypse” scenario, only with a hunger for blood instead of brains. Typically, Science-based vampires are unaffected by any routine faith-based energies. They may or may not be affected by “typical” vampire weaknesses, such as sunlight, wooden stakes, garlic, and holy water depending on the side effects of their creation method.
Vampires with magical origins are almost universally human beings altered by some magical force, typically classified as “the curse of vampirism.” Wizards chanting around an altar and casting spells at the subject are the stereotype of this particular breed, although the hapless apprentice fooling around with magics best left alone may also find himself suddenly afflicted. This type has a wide variety in powers and abilities, ranging from the classical necromancer in a tower to the dust-stirring ghoul living in catacombs. In most cases, the subject retains his or her normal mode of thought and is faced with the prospect of dealing with a new set of conditions for living. This type of vampire may have a poor reaction to the effects of faith, possibly due to a heightened sensitivity to such energies rather than any actual animosity on the part of a deity. (But see Spirit-based vampires, below.)
The variety of ways vampirism can be inflicted magically make it difficult to easily pigeonhole this particular type. The key characteristic, however, is the subject is a human being altered by some force, rather than by a virus or deity or other influence. Eric would be classified as a Magical vampire; his vampirism is the result of an infection of chaos forces in some long-distant Patient Zero and spread from person to person.
Vampires with their origins based on some sort of spiritual effects are individuals cursed with vampirism by some entity. They are similar in many respects to Magical vampires, but the motivating force behind the transformation is a supernatural entity, usually malevolent. Count Dracula, arguably, is a spiritual-origin vampire, cursed by God for his repudiation of all things holy. Another variation on this type is the human possessed by some spirit, such as a demonic entity. Typically, this type of vampire is the most sensitive to the energies of other supernatural entities, hence the effects of religious artifacts on them.