Challenge of this is to make a plausible "Illuminati", only this time, I'm not talking about the ACTUAL faction that existed before being disbanded in the 1780s but the Malign conspiracy existing in the minds of the insane that wants to take over the world.
How could such a faction exist, and gradually exert it's dominance as long as it wants?
What is the plausibility of such a faction existing, and how could it come to power? Remember, the Illuminati in these conspiracy theories is a covert shadow group manipulating governments so don't expect it to go all out like the Draka or something.