In the early days of the Last War, Cyre relied on House Phiarlan to gather intelligence but knew that such an arrangement with a dragonmarked house might not last. Over the course of decades, Cyre began to develop its own spies, the agents of the Fifth Crown, who were largely made up of Assassins, Masterminds, and a few Arcane Tricksters trained to infiltrate enemy territory. In the wake of the Mourning, the fate of the Fifth Crown remains unknown. Most people assume the agency was obliterated with its headquarters, but there are conspiracy theorists who say that agents of the Fifth Crown have worked their way into secure positions across the Five Nations, and that they are simply waiting for Prince Oargev ir'Wynarn or another Cyran leader to devise an effective way to use them. Until then, they might be the neighbors, postal carriers, teachers, or even community leaders, biding the time until such time leadership activates these pocket splinter cells.
Source: Morgrave Miscellany