[Agema]

Terrorism would essentially be represented by events that cause unrest. For instance, invade a province that (presumably) before had 0 unrest, you'll probably see it has 20-30 after you took it - presumably angry locals not happy with the disturbance and change of rulership. You also get a bit of unrest in provinces with enemy Dom, I think. Others have explained events, spies, assassins, patrolling and so on.