This started as a Whoblog post, but as it's very much on the outside of Doctor Who it migrated to the more general blog.
Who is the Mysterious Woman passing through every first issue of the New 52? Who is the Observer? Who is the source of the classified documents? Who is the old man with the map in the corner of the tavern?
The unknown is a key part of many genre settings, and it can be spun in unexpected ways. The X Files thought a lot about why Deep Throat and his successors passed on secret information, while The Old Man With The Map is largely dismissed as a cliché but could become rather interesting if he were treated the same way.
What are their agendas? What are their origins? Why are they being so mysterious anyway?
And how would those on the outside perceive the PCs and their circle?