Vampire

I don't like the D&D 5e vampire lore so I made my own.
Vampires are intelligent undead that are found all over the world. They generally avoid drawing attention to themselves so as to avoid being hunted. The total number of true vampires in the world is unknown but estimated by experts to be between 100 and 300. Vampires regenerate, can spiderclimb, summon animal minions(bats, rats, and wolves and have increased strength, speed, and constitution. They are very powerful and generally are only hunted by experienced members of the church and Order of Mizzet.

Weaknesses

Vampires have several weaknesses. The first of which is sunlight. Being in sunlight causes vampires pain, deals damage to them, and stops them from regenerating. The same is true for running water. They feel pain, take damage, and can't regenerate, as if the water is acid. Notably, it was recently discovered by the Order of Mizzet that oceans and lakes do not count as running water, neither does just pouring water over their hand. It seems to be restricted to rivers and babbling brooks. The exception of course is holy water, which deals damage(though less than sunlight), causes pain, and stops them from regenerating. Wooden piercing weapons don't deal any extra damage but do get around their non-magical damage resistance. Vampires are also unable to enter the home of a living humanoid without an invitation, of course most will just charm you into inviting them in. Recent experiments conducted by the Order of Mizzet found that temporary living spaces like tavern rooms or tents do not count as homes, but if a innkeeper lived in the inn they ran full time a vampire couldn't enter their room but could still enter the guest rooms. Similarly, if a home has a shop on the bottom floor the vampire can enter the shop but not the living area upstairs. Additionally while vampires don't need to sleep they do need to rest and for four hours a day enter a trancelike state similar to elves. Generally, this is done in their coffin, traditionally between the hours of 11am and 3pm, when the sun is high. This rest does not need to be in their coffin but a certain comfort is reported that isn't found when resting elsewhere.  

Killing a Vampire

When a vampire is brought to zero health they turn into a mist. This mist then retreats to the vampire's coffin. If the mist in unable to reach the coffin in time(generally about 2 hours but can very based on age), perhaps because the coffin is too far away or they are trapped in an airtight space, the vampire is destroyed. If the vampire is in direct sunlight or submerged in running water when it falls the mist is also destroyed. If the vampire falls in the shade the mist can travel through sunlight to get to the coffin but while doing so it is vulnerable to attack and dealing enough fire or radiant damage to it will kill it. If the mist successfully makes it back to the coffin it spends 1 hour reconstituting itself into the body of the vampire. After 1 hour the vampire rises with 1 health and generally gorges itself on blood to regain its vitality. While the body is reconstituting you can stab it in the heart with a wooden stake to kill a vampire. Stabbing it with a silver dagger instead paralyzes it and stops it from rising.

Basic Information

Anatomy

Vampires appear as they did in life, with the exception of their eyes. The iris of a healthy vampire is blood red. This effect can be covered with simple illusion magic. A vampire's eyes also revert back to whatever color they were in life if the vampire hasn't had human blood in over a week.
  A vampire's trademark fangs are retractable and can be made to look like human canines but can sometimes come out unintentionally when a vampire is especially hungry or faced with strong stimulus. Such as an open wound gushing blood right in front of them. Vampires' fangs are not straws, they are simply puncturing tools from which they suck blood. Their increased strength allows them to suck the blood harder than a human could but they still prefer to puncture an artery to make the drinking easier, even better if the victim is living and the heartbeat is helping force the blood out. 
The paleness found in most vampires is a side effect of them avoiding sunlight for years and years. Thus a newly turned vampire is just as tan as it was in life but as it spends more and more time indoors the tan will fade like it would with any normal person.

Genetics and Reproduction

Vampires cannot reproduce with other vampires but can reproduce with humans. The children of such unions are born Damphir, a type of proto-vampire that has a bite and taste for blood but lacks a true undead nature.
There are two ways that vampires create other vampires, both require the target to be drained of blood by the vampire and buried. This turns them into a vampire spawn, a type of undead thrall with grey skin and a limited version of a vampire's powers. Vampire Spawn are all subserviant to their master. Spawn can become true vampires in two ways, the first is if a vampire feeds its blood to a vampire spawn it created. The second way, which was discovered only recently by the Order of Mizzet, is for the true vampire that created the spawn to die. When this happens all vampire spawn they created become true vampires. This is one of the reasons vampires avoid killing each other, you never know how many spawn could turn into potential problems.

Growth Rate & Stages

Vampires don't age or grow, thus a child who becomes a vampire will have the body of a child forever.
There are however generally stages of vampirism. The first, which lasts about a year, the newly created vampire is ravenous and can rarely control itself when an open wound is nearby. Most struggle with just having a living humanoid in the same room. Many vampires choose to keep one they have turned as vampire spawn for the first year so they can simply command them not to feed without permission. During this phase, vampires often form a sense of superiority and lose some of their natural empathy. It is unknown if this is magically done or if it is a simple psychological defense mechanism for when you start killing people.
The second stage is generally from 1 to 100 years after being turned. During this phase vampires generally learn to control their urges, for the most part. Many who were good-aligned before being turned, regain some semblance of their humanity. Rarely going all the way back to good but perhaps ending up lawful neutral. Others simply graduate from ravenous beasts to cold hearted serial killers.
The third and final stage is generally from 100 years after turning and onward. At this point, many of the people vampires knew in life have died. Most stop seeing people as equals, some see them merely as livestock, while others see them as pets or children. They become patient and cunning in a way that only comes to those who have lived long. Their plans are measured in decades and they have mastered controlling themselves. When a vampire reaches this stage, 100 years after turning they are considered an adult by vampire society.

Dietary Needs and Habits

Vampires and vampire spawn generally prefer to drink a gallon of blood per day, though they can survive on as little as a pint per day without negative affects. Older vampires can sometimes bend this rule, surviving for over a week without blood or ill effects. Vampires and vampire spawn can feed on animals and other non-humanoid creatures with blood. But if they do so for more than 3 days their regeneration is halved. On the 7th day without humanoid blood they loose access to many of their powers including all of their regeneration, the ability to shapeshift or become mist(except in the case of misty escape), the ability to summon minions(rats, bats, and wolves), and they lose a portion of their strength and speed(though they are still stronger and faster than most humans).
Vampires and spawn that don't drink any blood suffer a point of exhaustion each day. Drinking at least a quart of humanoid blood removes any amount of exhaustion gained this way. When they reach 6 levels of exhaustion they do not die but instead simply suffer all the exhaustion penalties and are in extreme pain. Slowly over the course of a year, they will petrify, becoming hard to the touch and unable to move, during such time their mind shuts down as if asleep. When this happens they can be cured by even a drop of humanoid blood which brings them back to the 6 levels of exhaustion state. As such a vampire really only needs 1 drop of blood a year to "survive" but it is an existence of agony known to drive them mad.

Additional Information

Social Structure

Vampires that know each other are organized by age. As a general rule vampires get stronger as they get older. This is due to two factors; experience, a longer life means more experience and generally more combat ability; and magic, as they live longer their bodies become accustomed to the magic that gives them undeath and are better at harnessing it naturally, leading to an increase in strength, dexterity, and constitution over time.
Vampire spawn are always below true vampires on the totem pole, partially due to their place as slaves and partially because the growth in their power over time is exponentially slower. It is possible for a new vampire to be more powerful than an older vampire, but this only happens when the newer vampire was already formidable in life and could have beaten the older vampire without undead powers. Such exceptions are rarely considered by vampires and generally have no bearing on social hierarchy.

Perception and Sensory Capabilities

Vampires have slightly heightened senses that many older vampires have honed to extremely high levels. The average newly turned vampire is only slightly better at perception than it was in life. The exception is with blood, most vampires can smell fresh blood at 100ft away, for older more practiced vampires this range can extend for hundreds of feet. Many experienced vampires can tell the race and sex of a creature whose blood they taste and develop a preference. Often the preference is whatever the vampire was in life, an elf vampire often preferring elves or a tiefling preferring tieflings, though this isn't always true.

Civilization and Culture

Courtship Ideals

Many vampires are single and feel no need for romantic entanglement. If they form a partnership it is usually with other vampires, only they would understand their lives and ethics systems. The need to reproduce is something inherent to being alive and is not present in vampires. Those who wish for children often satisfy that desire by siring a new vampire. Others abduct and charm a human surrogate into their bed creating a damphir child that the vampire will turn when they reach physical maturity.
Those that fall in love with humans will often have children with them before turning them so that they can be together forever. In that case, the process is basically the same. Even though the bond between scion and sire is somewhat paternal in nature there is no weirdness around marrying your scion.

Culture and Cultural Heritage

Many vampires view their sire(the vampire that created them) as a parental figure. A vampire's sire is by definition older than them, creating the power imbalance, and tradition dictates that a sire educate their scions in vampire ways.

Common Taboos

Killing another vampire is considered Taboo among their kind, this is partially due to them seeing their own lives as more important than humans and partially because killing a vampire turns an often unknown number of vampire spawn into true vampires, which can cause problems. Those who make a habit of it are often ganged up on and killed themselves.
It is also Taboo to kill a humanoid who is claimed by another vampire without their permission, as this is the equivalent of both stealing their food and killing their pet. Vampires can imprint a kind of magical scent on the blood of someone they have claimed but can only claim 7 people at a time. Its rude to eat another vampire's livestock as well but it isn't nearly as important. 
Vampires also avoid making messes in each other's territory, a roaming vampire might otherwise cause problems for one who has set up a permanent location.
It is also taboo to abandon your spawn or newly created scion(a true vampire you have sired). If abandoned many struggle with the first year especially. It is a sire's duty to educate their scion's in vampire lore, traditions, and abilities.

History

It is believed that the first vampires were created by the human wife of one of the 9 dark wizards that slew Niv-Mizzet. He was an elf and had recently become lich, and was facing immortality without his beloved. She was a powerful wizard in her own right, though not one of Mizzet's apprentices. He taught her the Lich ritual and she successfully pulled it off shortly before his death. After he died she was distraught and vowed that none of her loved ones would ever die again. But their children had no aptitude for magic and she doubted they would reach the level required to perform the Lich ritual before their deaths. So she created a new ritual, one that stopped their aging, gave them strength, and let them heal. The ritual required them to drink the blood of a human sacrifice and created the first vampires. It is unknown if the weaknesses vampires suffer were on purpose, an accident, or an accepted cost of immortality. They had 5 children and so 5 vampires spread across the world, one of them known as Samuel the Slayer believed that his family had become monsters and tried to kill them all. And while he did succeed in killing many vampires his siblings and mother eluded him and eventually killed him, leaving 4 vampires and their descendants.

Historical Figures

Other than Samuel the Slayer most historically notable vampires have been villains.
Captain Marcos Soovere is a vampire pirate captain first heard of 600 years ago, who gained quite the reputation as a plundered of ships in the night. But many believe him to be a folktale told in the shattered sea. No credible sightings have ever been documented.
Count Allzorah was an elven vampire who briefly tried to take over Zirdy before he was killed by the Elven church in the year 670.
The Sumarrians have a mythical figure known as Onichi The Terrible, believed to be an oni who became a vampire.
It is also believed by some that Reginald Orzhov, the financial minister of Bradis and head of the Crimson Bank, is a vampire but this has never been confirmed. Though he is a human who has reportedly lived for over a thousand years. Some suspect this to be Bradis propaganda meant to instill fear of the bank.

Common Myths and Legends

They say that there were originally five vampires. Samuel the Slayer being gone, leaves 4 still out there. They are spoken of in reverent tones, age is everything in vampire society and they are literally the oldest.
The one that is most well known is Biblioth. He is spoken of not just by the vampires but also the mages of the world. He is believed to be the oldest wizard in existence. He has created a sort of cult known as the memorium. They live on an invisible floating mountain that Biblioth can move around the world. Biblioth is known to have a photographic memory and has consumed millenniums of knowledge. The wizards who study under him study in the hopes of gaining immortality, and to do that they need to impress him with something new. Something he hasn't seen before. His mountain lair is known house a magical library that is said to outshine The Order of Mizzet. Biblioth is rarely seen, partly because the church has been hunting him for 1000 years and party because he is always engrossed in his research. It may be centuries before he is seen in public again.
Next is Morien, a female vampire who typically lives in Zirdy. She tends to move around, never staying in one place for too long. She has many friends among the world's nobility and moves from palace to palace. Of course she uses aliases so most don't even know that the beautiful socialite they've been dancing with all night is actually several thousand years old. She is said to have mastered her charm abilities so completely that she can charm even those who should normally be immune, like other vampires. 
Abaddon now lives in obscurity. He once was the leader of powerful noble house and held the greatest number of human livestock. But rumors say he grew bored. He gave the noble house to his children and now holds court over only the undead. If there is a "King of The Vampires" it's him. He is a decent wizard but unlike Biblioth he is not devoted to it. He spent his eternity gaining strength, they say he killed giants in a single blow. He is brilliant, cunning, and possibly the strongest undead in the world. He oversees vampire politics and enforces its rules, though he himself is rarely seen. Being summoned before him is enough to make any vampire shake in their boots, but if you run you know he will find you, he always does.
Fumori is Abaddon's right hand. The only sibling to stay by his side. Fumori has mastered his mist form so completely that he can make attacks from within it and be nearly invisible. You never know where he is, never know if he's watching. They say that most of the time he doesn't exit his mist form, appearing as a swirl of shadowy mist, vaguely in the shape of a person.