Total Drama Dungeon!
The Guild Arcanum is the official organization that sanctions and regulates magical activity in the North American Empire as well as most European and North African nations. It is the direct heir of the Collegium Pontificum of the First Empire.
As an extra-national organization that wields immense magical power as well as having so many members highly placed within multiple governments, it is possible that the Guild is the most powerful force of the human world. However this is not an opinion that is voiced loudly – at least not where the agents of the Emperor can hear.