The Hunger is usually what breaks you.
It gnaws at you, screaming inside your head, constantly pressuring you to feed. If you give in, if you hurt a person to quench the ravenous need for blood, there might not be a way back. You'll become a monster - a hunter of the night, doomed to keep killing and feeding until they get you.
If you manage to ignore the overwhelming Hunger, and only feed on willing individuals and wild animals - there might be hope of an existence that can almost be called a life.
But the Hunger will always be there, taunting, waiting for that one time you will slip up.
Because you will slip up. We all do in the end.
Transmission & Vectors
A vampire's bite has some kind of magical virus. A person might get infected the first time they're bitten, but usually it takes more than one bite to infect a person. The more blood that is drained, the larger the chance - but if all blood is drained from the victim's body, there isn't any blood left to transport the virus through the body. In rare cases a fully drained body might get infected and become a vampire, but it's extremely rare and the vampire will wake up in a ravenous frenzy, attacking anything close by that might contain blood.
If a person gets infected with vampirism, they will die.
With most other conditions that would've been the end. However, vampirism is an undead condition, and these conditions usually start with killing the infected. It's after death the other symptoms appear.
The heart stops and blood flow halts. This leads to a much lower body temperature and sickly pale skin. The infected doesn't have to breathe anymore, but usually keeps breathing out of habit. The magic power inherent in the condition will keep the muscles from going into rigor mortis as long as the vampire doesn't go too long without feeding on blood. This magic keeps the mental processes going as well.
The infected will get a pair of fangs as the maxillary canines grow twice as long and become sharper.
The vampire's personality will often change slightly, not because the condition will change it but because the Hunger will make it harder to have a normal relationship to humanoids. It's hard to not act slightly strained among other people when you're trying to not eat them.
Sunlight won't directly turn a vampire into ash or set them on fire, but it will rapidly weaken them, drying out their body until they can't move. This will happen in minutes. A vampire can survive a couple of seconds in sunlight before having too much of an effect, but the longer the vampire spend in sunlight the longer it will take to recuperate from the damage. After about a minute the vampire will start taking permanent damage which will make its body stiffer and harder to move, reducing both speed and dexterity. Death is certain when sun exposure gets close to two minutes.
The lifespan of a vampire is in theory endless, but most vampires live short, frantic lives before getting killed after giving in to the insatiable hunger for blood. About half to two thirds of all new vampires will be killed during their first three months as an undead due to succumbing to hunger. Nine out of ten of the vampires that survive these first months will either die of starvation or get killed during the first two years. It is often said that a vampire has less than 5% chance to live for more than a couple of years - and reality has proven that it's a pretty accurate estimation.
Although old wives' tales swear to holy symbols and garlic to keep vampires away, the only way to prevent catching vampirism is to keep from being bitten by a vampire.
Outside Death's Table most people think vampires are a myth from stories meant to scare children. The few who know vampires even exist out there will most likely kill them on sight since they are considered evil creatures that prey on humans wherever they go. There is a certain truth to this.
In the Death's Table area, however, most people will leave vampires be as long as they behave. Smart people will keep an eye on the vampire if one is close, though.
Considering how dangerous a vampire can be to the general public there are some rules a vampire must follow. This is to keep both the vampire and non-vampires safe.
It is a well-known fact that any vampire, no matter how good intentions they might have, might lose control and feed on unwilling individuals. This usually leads to the victim's death. For this reason all vampires must stay inside Death's Table at all times so they can be kept track of. Outside the Table a vampire will be killed on sight.
A vampire should never feed on an unwilling humanoid. If it's found out that a vampire has been feeding on unwilling humanoids the vampire will be killed on sight.
A humanoid is considered willing if they have been informed of the risks of being fed on by a vampire and consent to this while not under any kind of influence or mind-affecting effect. Such influences or mind-affecting effects might be, but are not limited to intoxication, mind control, charm magic, possession or hypnosis.
Listen, if I find out that any of you leeches break the rules I will personally rip you to tiny pieces. I've worked extremely hard to get the Necromancers to let us live in the first place, and even though you might feel the rules are unreasonable and an attack on your freedom, remember that it's either following the rules or be killed. I don't know about you, but I'll rather live with these rules than being hunted and killed on sight for merely existing anywhere else.