Inquisition
From the White Wolf Wiki, the most complete White Wolf reference
The Inquisition is an organization within the Roman Catholic Church tasked to rid the world of evil and heresy in all it's forms in the name of God. This can include practicers 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 the best at fighting supernaturals. The Society has access to millenia 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. For example, Demons can submit to a test to determine if "they seek redemption" but failing the test means they are not simply killed but are literally erased from existence.
