Vampires are creatures that have a need for lifeforce energy. They take it by engaging in energy work, by drinking the lifeforce energy contained within blood [which is done by drinking blood literally or psychically without puncturing the skin of the blood source], and by absorbing energy from crowded public places. For additional energy, vampires take energy from nature. Failure to "feed" causes vampires physical and psychological problems.
Blood compacts more lifeforce into more dense spaces than feeding on energy not contained within blood. Consequently, vampires generally drink only drops of blood at a time.
Vampires that only intentionally drink blood take in energy during intimacy and vampires that only intentionally take energy wake up with the taste of blood in his/her mouth; so the spiritual [energy] and physical [blood] aspects of lifeforce can't really be separated.
The most potent kind of energy is energy inspired with the emotion fear, so vampires tend to engage in sadomasochism, as it's a venue for inducing fear in a controlled [and thus safe] situation. Sadomaschistic practices are also an outlet for otherwise suppressed primal instincts.
Humans and human-like creatures that are partners of vampires for extended periods of time take on vampiric desires and practices although their health is unaffected when they don't feed. They're called sympathetic vampires.
Vampires use the word "immortality" to mean reuniting with the souls of vampires time and time again on earth or in the astral realm [they choose to live on earth sometimes to learn lessons regarding how best to serve the greater good, and other times they choose to stay in the astral realm after death during an incarnation on earth because in the astral realm all knowledge is known and all pleasures are greater]. Immortality to a vampire evokes images of falling in love with the same creature, or falling back on the support of family, reincarnation after reincarnation, regardless of geographic location and societal prejudices.
All wounds heal with time in the astral realm, but a vampire remains a vampire after each incarnation on Earth, so it stands to reason that vampires are meant to be designed this way.
Vampirism is a religion whose denominations [called spiritual vampire Houses] are any structured beliefs that are centered around vampires. The stipulations for structured beliefs as far as vampirism is concerned are unity of ethical codes and beliefs about vampires; other components may be added optionally. I know of absolutely no vampire House that involves worship of any dieties. The closest semblance to diety worship is using certain dieties as rolemodels. Therefore, other religions can be used in conjunction with Vampirism rather seamlessly.
Vampires use their powers to cleanse individuals [by "individuals" I mean vampires and other human-like creatures] of negative energy and clearing their energy blockages, setting the static energy of individuals to regenerate so that the individual has more energy and healthier energy [which causes the vampire to feed while symbiotically helping someone else], and beridding individuals of their negative emotions.