This is a major part of a story I'm working on called "Red Wind" and I'd like to explain how it works. The Bureau manages the somewhat delicate balance between realms, especially ours. It doesn't try to keep it secret or anything, it just keeps one realm from polluting another. To do this it employs people from the earth, exclusively, to fill the many roles it has created according to its own laws. This is what I'll explain in depth because there is a color code to its ranks evolving from the three primaries and elemental subtitles to indicate an operative's area of authority (ie Red Wind means the op. is a nullifier set in the east). Every operative can move up and down the gyres, their ranks as I've mentioned before. Now here's the run on the colors. 
 
1st Gyre
Red: The Nullifiers are like cops for the realms, they take down trespassers, prevent macabre rituals, slay demons and what not. Their methods are based on "bent" magic, magic that requires a medium, in Wind's case a bow to shoot arrow shaped spells, but I promise NO WANDS. Maybe a scepter but NO WANDS, I don't like them. They also have special tattoos, called marks, that give them access to single, usually powerful spells, and guns, anti-magical guns. They are mainly stationed for earth but are also incorporated to other realms for their strategic expertise. 
Blue: Path Finders are like detectives or can be put to escorting beings in and out of the earthly realm. They use direct magic but not much of the deadly stuff to capture suspects or actually, as the name implies, find paths in a journey or case. They have no armaments, no need with direct magic anyhow, but are equipped with a bestiary, lexicon, atlas and forgotten languages all held within their minds. They can move throughout most realms with the permission of the Bureau.
Yellow: The Messengers are what they are. They have the most efficient transport spells at their disposal and not just teleportation, they need intangibility and foresight to avoid any risky interventions. They are only used to transport very crucial messages and guide travelers who have payed for it. For diplomatic reasons they do not have weapons but they can place protective/apprehensive seals on anything or anyone they transport. The Bureau has also insured them with "The Lightning Sanction" which brings an obvious shock to any creature that intends to harm them. They have much knowledge of the winding ways between the realms, more so than the blues themselves. 
 
Well there's 1st Gyre and I'll bring you the others in the weeks gone by. Hope you like and please share your thoughts in the comments. 
The Bureau of Mystic Equilibrium Part 2 
The Bureau of Mystic Equilibrium Part 3