These are Dhampiri, and not quite so. Warning: Possible thread split.
Created by Captain Penguin, manfred and Siren.
Vampirism is a supernatural teaching. It is the philosophy, nay, religion of those unwilling to obey the truly important rules of the universe. Mortals become old and weak, and die in the end - that is one rule of the universe. Vampires are actually supernatural rule-breakers. Immortality is but one goal, and there's many more annoying rules to be broken or by-passed.
The specific thing about this "religion" is that one could become a God himself in the end. And vampires seen in this light are not some blood-sucking monsters (well, they are), but philosophers in their own way. Theirs is not a solid church, but rather a couple of splintered sects that differ on the teaching, ways, Blood Riddles,etc.
Note to Ur (the first vampire, that vanished in the end): One theory is, that he become so powerful, and independent on the rules of this universe, that he has simply gone beyond it, and made his own universe. May be a legend, a secret myth of some sects, or the truth.
Why do vampires need blood?
If vampires want to avoid Death, they have to take Life, because theirs is not sufficient. Of course, they have to do this only UNTIL they become more powerful, and truly self-reliant.
The Bite is actually a ritual transfer of the Life Force. Some victims claim it is an ecstatic experience, some are horrified from it, a few unstable natures were driven mad from it. The loss of one's very Life is certainly unsettling, and can make a victim easier to persuade, because...
These vampires don't spawn.
Correct, being bitten doesn't turn you into a vampire, it is a teaching that has to be learned. Consequently, vampires have to have students to multiply.
So as a bonus, they have to parley with people, they have to seduce them to become apprentices. Thus the good ole villain talking to heroes cliche comes to life! They explain themselves... let people feel what it means to loose their Life (bite them), and warn them it will dwindle from then on all their lives... until they die.
But if they support the vampire, he will save them... and give them the ticket to earning immortal life. There is nothing about tempting heroes to turn to the Dark Side, right?
Note: imagine a special gentlemen's club, admission by invitation only
The sun defines the cycle of Night and Day, a rule vampires cannot avoid in any way. Also, their very existence is a lie. Therefore, by entering the sunlight, the Vampire must confront the complex lie he has used to shield himself from death. 'The Light of the Sun, being the natural light of the Universe, Illuminates Truth and Banishes Illusion.'
But their belief is, one day they will become powerful enough to avoid it.
Note: But the moon changes constantly, defying rules, so they can tolerate Night. In addition, eclipses might be of the holiest significance- the darkening of the sun, a sign that He is calling out to the strong.