Here's an idea I've been kicking around for a campaign where everything goes to Hell in a handbasket. The Solar System erupts in total war, strategic weapons are tossed around like candy, terrorism and sabotage become commonplace, and social collapse occurs in others. And that's not getting involved with the Factors, TITANs, or the like. The way it would start off is after a Barsoomian terrorist attack uses devices made from Titanian nanofabbers (perhaps a questionable claim), the Planetary Consortium and Jovian Junta attack the Commonwealth. The Titanians begin debate unleashing their strategic assets and weapons, but they know they're outgunned and would be annihilated. So, they resort to sabotage, unconventional warfare, netwar, and what they do best. The other autonomists either join in or head for the edge of the system. Extropia itself becomes an urban war zone under martial law as mercs, partisans, and anyone stuck in the crossfire slug it out (assuming someone doesn't just slag it). The Jovian Junta fears the PC would betray it as soon as the campaign ends, so they begin preparing their own aces in the hole in the form of more secret police, nukes and antimatter warheads, and secret projects involving seed AI and TITAN relics. The Tharsis League on Mars faces near civil war and unrest between Barsoomians and the PC. Terrorism, guerrilla warfare, massacres... All of these are done on all sides, and then some. With the concentration on the war, hardly anyone is left to guard the TQZ... The Morningstar Constellation has had some problems involving saboteurs attempting to bring down their aerostat cities. It may be some anarchists, or it may be the PC using the chaos of war to remove a potential rival, one aerostat at a time. A major aerostat city drops to the ground, and it is not the only one... The LLA, technically neutral in the conflict, faces an uprising of the clanking masses. Opportunistic raiding by the criminals and pirates in nearby habitats adds to the chaos. While some strange activity is reported in New Mumbai, more alarming is the fact that large sections of the interdiction satnet around Earth suddenly start going offline. TITAN structures and machines roar back to life, and presumably TITAN spacecraft emerge from the holes in the fence... Meanwhile, the Factors seem to have converged at specific points within the Sol System, and are building structures of unknown function that have high energy emissions. No one is quite sure what these are for... Even the extrasolar colonies are not safe. Contact with colonies is lost as more and more are cut off. Reports of TITAN drones and exhuman infiltrators spread paranoia amongst refugees fleeing back towards Sol... So, if you want to bring doomsday to the Solar System, how would you do it?
—"Ipsa Scientia Potestas Est."