Many, perhaps most fantasy lands are monarchies, which can be ruled well when the monarch is a clever and able man or woman devoted to his or her people. But what happens when the monarch is ill, or is tyrannically cruel, or a young child, or is otherwise blatantly unfit to rule? How can he or she be dealt with without risking civil war as powerful nobles fight for the crown?
One of the current political paradigms of the Cosmic Era.
The plague of the Petroleum Era, the true bane of organized government
Animals have parasites and diseases, so do plants, there are even bacteria that cann dissolve oil spills or plastic or what have you - why couldn't there be a disease living off magic - a magic item could be infected, losing power and speading the plague to other equipment it contacts, while a magic user would slowly lose his powers and contaminate all he works with or casts a spell at...