Vampires are born out of a fundamental change which can occur in the physical bodies of creatures which possess a soul. In most mortals the soul is the fundamental source for action, creating the original impulses which eventually become the person's acts. It is also a passage through which the creature can gain a small amount of the infinite power underlying the universe, power which is necessary for the functioning of a self conscious being. A vampire is born when a mortal creature undergoes a change which causes the sensual physical body to revolt against the soul, usually expelling it, and taking control of the creature. The actions of the being are then controlled by either the remaining physical brain, the remnant of the soul, whatever caused the expelling of the soul, or a conglomerate of these forces. It is this emphasis on the physical body to the exclusion of the soul, which causes many vampires to be obsessively sensual and addicted to their own suddenly intense perceptions.
There are many things which can cause a creature to become a vampire. These include certain forms of intimate demonic possession, various viruses, the casting of spells to become a vampire, or mental disease. Each of these causes has its own peculiar nature, and can result in very different outcomes for the victim. The change into a vampire is almost always accompanied by physical changes in the creature's body. The most common of these is a removal of the ability to feel pain, and a fundamental change in their perception of the world. These are caused by the sudden lack of soul, which influences the way everything looks and feels. The immortality of the creature comes due to a perceptual change. The body in complete control of itself does not choose to harm itself with entropy, and so stops doing it. However it is the soul which provides a creature with true wisdom and this form of immortality almost always results in major psychological problems. While immortal, eventually almost all vampires end up committing suicide due to the pressure of their own thoughts.
Changes such as an increase in strength, the ability to fly, psychic and telekinetic powers, and magic abilities are fueled by a power source which accompanies the transformation. As such these abilities are dependent on the amount of energy within the being, and will be increased or decreased by this factor. Energy is a major problem for vampires, who have to fuel a self conscious existence without the benefit of the soul's pathway to the infinite power source. If a demon initiates the change, then their inherent power will fuel the initial act. If the change occurs due to a mental problem, or a mental problem caused by a virus, then the remnants of the soul and the body itself will have to fuel the initial change. This often results in vampires of very low consciousness and power. Later energies have to come from another source, as even the initial power of a demon can not fuel a conscious being for long. This power is often gained through the drinking of the blood or souls of other self conscious creatures. Unfortunately the drinking of a soul, or soul blood, will only give a creature a limited amount of energy, requiring that the vampire repeat this act on a regular basis to survive. The need for energy can become an obsession in vampires, overwhelming any sense of control and self they may have once had. If the need becomes too great, it can utterly destroy whatever mind remains in the creature, turning them into a zombie.
Some experiments have been done with plasma, as well as nuclear and subatomic energy sources as a way of fueling vampires. This technology is still in its infancy however, and most of the vampire test subjects claim that these methods are still too weak to effectively sustain them.
Methods for becoming a vampire:
Intimate infection from a demon: When a demon infects a mortal in such a way that they bind with the physical body of the creature, they can often pry the soul out of control of the body and permanently remove it. The power of the demon fuels the initial removal of the soul, as well as the first few hours of action. After this, most vampires will require the blood or soul of other conscious beings. Over time the demon will become more efficient at extracting the energy from these sources, and will require less. However initially, the need will be quite great.
This method of infection can also be transmitted to other conscious beings through the sharing of blood. In this way the demon within the initial vampire can multiply itself. The power of the second vampire will be slightly less then its makers, however over time it will also increase. There is also some speculation that when the initial vampire is destroyed, if the demon is eradicated with it, that all of the vampires born of that demon will also be destroyed. These vampires tend to be the most powerful, and possess the strongest attributes. This is because the energy of the demon fuels the initial transformation, and the first few hours of existence. The demon also helps the body to become accustomed to its new existence, and can synthesize the souls or blood of other creatures, making it a useable source of energy.
They also make it easier for the body to tap into telekinetic, psychic, and magical powers, as well as the new physical power within its body. Infection from a virus: Some viruses can cause a change in the body which destroys it in such a way that the soul flees, but the physical brain retains some control over the creature's actions. Initially such beings will be extremely weak and may be mistaken for dead. However, if they gain a source of energy, and a way to synthesize it into something they can use, they may be able to cobble together a consciousness. Their energy source may be the blood or souls of humans, or might be some other form of magic or chemical energy. These vampires are marked by weakness, and a lack of consciousness. They are often compared to zombies, with the main difference being that vampires do not seem to degenerate after the initial change, while zombies are in a constant state of decline.
Vampirism by mental disease - In rare cases a person's physical mind can become obsessed with the sensual body to such an extent that it begins to revolt against the creature's inner soul. This is usually a violent struggle, and can be very painful and difficult for the victim. As the soul is removed the creature begins to require alternate sources of energy to fuel its consciousness. In these scenarios, blood or souls are as likely as any other source to become the fuel, as the creature does not possess the ability to synthesize blood into a useable form. Some cases have been observed where vampires of this type become voracious eaters, others draw their energy from fire, and others use magical means to fuel themselves.