- Inquisition: The war humans waged on vampires in the thirteenth, fourteenth, and fifteenth century.
The Inquisition is an organization within the Roman Catholic Church tasked to rid the world of evil and heresy in all its forms in the name of God. This can include practitioners of witchcraft, vampires and possibly, all supernaturals. They probably know more about ALL supernaturals, and how to (permanently) destroy them, than any other organization (mortal or supernatural).
Followers of the Inquisition are referred to as "inquisitors" and are generally mortal, though there are exceptions (naturally no such exceptions have been acknowledged by the Inquisition).
The primary subset of the inquisition tasked with the pursuit of supernaturals is the Society of Leopold. The Society of Leopold makes for a major threat to any group of supernaturals for the simple reason that its members are among the best prepared for fighting supernaturals. The Society has access to millennia of knowledge about supernaturals, are trained specifically to fight them, and have equipment specialized for combating each type of supernatural.
Some supernaturals can gain the Inquisition's "approval" to exist and not be terminated on sight by the Society of Leopold, though the tests employed to gain this approval tend to be of an extreme nature. Failing the test usually results in death, or worse. Despite fighting the supernatural and evil in the name of God, they are or most are not moral but fanatic and don't usually care whether or not the creature they are hunting is good or evil. They have at times killed innocent peoples due to their fanatical view of the world.