From SuspireWiki

Ostiary is a position within the Lancea Sanctum that translates roughly as "Keeper of the Door." The position is a martial one, and involves protecting the city (in the case of a Sanctum-dominated city) or Lancea Domain against outside influences. Typically, this involves patrol, investigation, and elimination of any threats discovered. The Ostiary reports to the Bishop or the Sheriff, again depending on how dominant the Sanctum is in any given city. The position of Ostiary carries with it some respect, but not enough to really increase any given Kindred's Status.

Past and Present Ostiaries in Atlanta