A Game with No Rules

The Empire is splitting at the seams. The Great Houses refuse to obey the Throne World and have begun to conduct increasingly independent politics. Sensing the weakness of the central government, even the most loyal star systems of the Imperial Core are refusing to take orders from above. Is this just a string of coincidences, or a coordinated campaign? Can a disjointed humanity rally around a strong leader to deflect an alien invasion? Who of the many figures in intergalactic politics can rise to this challenge? And is there a basis to the creeping rumors that some influential aristocrats have joined forces with the enemy and allied with the aliens?