These are the basic rules for vampires, both NPC and PC:
If a grapple or Charm is successful, a vampire may automatically bite the next round (d4hp damage) and will drain a level (or HD) from his/her victim, adding its class levels and hit points to his/her own.
A vampire may not do anything else in a round where s/he bites.
If s/he successfully slays a victim in this way, the victim will become a vampire of the same type of the lowest rank (pawn or ace). It will be subject to the vampire’s will until she is permanently slain. Unless the campaign is cool with vampire characters, a character has 42 hours to find a way to reverse the process (see below) before going mad with bloodlust.
Direct sunlight or a silver or wooden stake through the heart will slay a vampire permanently.
Garlic will hold them off for 1 round, eating it causes d4x10 damage.
Drinking holy water does 7d6 damage.
The touch of holy water or silver causes d6+1hp damage.
They are immune to poison, falling damage, and all forms of mind control (other than the power of a superior vampire or magic that controls undead). They cast no shadow and have no reflection.
Female vampires may walk in the daytime so long as they employ parasols marinated in unholy water.
The severed tongue of a virgin, if placed in a vampire’s mouth, will do 2d10 points of damage.
Transforming into an alternate form does not take an attack/action but it must be the vampire’s turn (i.e. a vampire cannot willingly transform in response to character action until its part of the initiative cycle).
A natural 20 rolled with a wooden stake on a vampire by a character announcing their intent to stake should be considered a stake through the heart, a failed stake does no damage.
If the vampire is being grappled or otherwise restrained by two or more limbs, a modified 22 or better with a wooden stake on a vampire by a character announcing their intent to stake should be considered a stake through the heart. For these purposes, the attacker should receive a +2 per limb restrained. Note however that most vampires will transform at the first opportunity if restrained.
Vampires are worth zero experience points unless permanently slain, not just removed temporarily as obstacles by reducing them