swam

Ok so I am working on a book that needs some good conspiracies to drive it. I need something that could be worked back to the time of Rome. My basic idea so far without giving the whole plot away is that the roman senate went underground before the fall of the empire and is running the world from behind the scenes. I want to be able to have a good history for this shadow government and its opposition. I decided this might be a good place to start. So any ideas, theories, or other places to look would be awesome!
thanks in advance.
as a side note, I want to avoid all of the common and above the radar stuff like the free masons and the Illuminati. the knights Templar are also overused in fiction.