It's true name is unknown even to it's members and is just simply referred to as "The Guild" however Historica Ordinis has it officially listed as Occula Furem.
It's members operate in secret gathering inteligence, performing assasinations, and otherwise doing whatever it takes. All in the name of "The Greater Purpose" of which no one is sure of what that "purpose" even is. Orders are passed typically through dreams of a darkly robed figure simply know as Unknown speaking in a voice of whatever language is native to the agent. Usually it's presented as a male voice but there have been times where a female voice has been heard.
Each member of the guild has been recruited by the voice with many being "saved" usually through life threatening situations where they miraculaously survived.
Rhogar Ellis recorded in his journal before his passing during the Great War of Taran that when an airshiup crash landed on the building he was occupying he was teleported after agreeing to be saved by the voice. This however is the last entry in his journal and any recorded activities.