A vampire hunter is an individual that hunts and kills vampires.
There are countless other universes existing congruent to our own. In these realms, physical laws as we know them do not pertain. Since time immemorial there have been intrusions between our universe and others. From these intrusions have emerged countless energies and lifeforms.
These various extradimensional lifeforms and energies are responsible for the multitude of "supernatural" creatures such as werewolves, ghouls, banshees, demons, and others. For over a thousand years, the supernatural creatures that have posed the most dangerous threat to humanity have been vampires. A vicious predator, a vampire is actually a human corpse that is possessed by an extradimensional entity that has granted it various superhuman abilities and given it a compulsion to feed on the blood of humans. For as long as these otherworldly and malevolent beings have roamed the Earth, there have been those that hunt them in order to protect and defend humanity.
The legacy of modern vampire hunting begins in 1095, when a group of Knights Templar were attacked by a band of vampires while on their way to the Crusades. Of the thirty Knights, one-hundred and fifty infantry and various auxiliaries only a dozen survived. They carefully buried their own dead (with proper precautions to prevent them from rising as the undead), wrapped the vampire remains and headed straight to Rome. They presented their findings to the Pope and his aides who already knew of the existence of vampires and other supernatural creatures. The twelve Templars begged for permission to begin a Crusade against these foul enemies of humankind. Their request was granted and they were re-christened "The Holy Order of the Venator Knights" answerable only to the Pope.
The Pope asked wealthy lords from Christian nations to assemble armies to join in the war against these unholy creatures. After training, the lords were welcomed into the Order in a solemn religious ceremony. The Order filled its armies with volunteers who were given plots of land in return for their services. They were granted sweeping powers with regards to their calling. They were allowed to read ancient church records and to conscript Knights and Priests from other Holy Orders. The result was a group of fanatical, knowledge, well trained and well armed men dedicated to the slaying of every last vampire.
The secret military campaign, known as the Vampire Crusade, was a modest success. Each new outbreak prompted another Crusade, and the battles went on for almost 300 years. After the Vampire Crusades were over, the Venator Knights lived on in the form of medieval Vampire Hunter Guilds, which were organizations of men trained in the art of fighting vampires. This extraordinary band of noble miscreants tracked down "nests" of vampires and destroyed the infestations for profit. Paid by both the Vatican and the people of the towns and cities who called on them for help, vampire hunters led good lives when they were between jobs. This trade, like others of that time, was most often passed on from father to son.
In modern times, vampire hunters exist as a network of highly skilled mercenaries dedicated to the elimination of all vampires, although their work does sometimes cross over into other areas. Financed by a branch of the Roman Catholic Church, they are organized into small teams (about eight people) who use an array of high-tech weapons for their fight against the powers of darkness. While they have contacts with the Vatican and can use their resources, this usually just means records and information, and in the field they are usually on their own. The teams are named after their leaders, such as Team Jones, Team Smith, etc. Most teams travel around a country rooting out the undead from nests. However, there are some teams that have been assigned to a specific place. All teams are directly supervised by a Cardinal.