Like the Imperial Legate of Rise of Kings, the Terrorist is a unit that is meant to destroy and sow confusion amongst your enemy's ranks. He is essentually in effect what we would call a saboteur or an assassin, armed with a short-range, slow-firing but powerful pistol, as well as bombs for destroying artillery and buildings, with a propensity for being able to kill Workers, Generals and Patriots outright.
Terrorists like Spies usually are invisible to most enemy units, excluding a select few including Scouts, Spies, Commandos and light cavalry, and all come with the ability to set bombs in place. Should the need arise, their concealed revolvers makethem highly useful as assassination units or as a distraction. A few terrorists running amuck in your enemy's cities can cause disruption at a level sufficient enough to keep your foe off balance for a while. Even so, they are only support units, and clearly are not suited for the job that military units can do, for one thing if spotted they can easily be ridden down by cavalry, notwithstanding their ability to kill or inflict serious harm. It is thus best for you to use these units in tandem with other agents, most notably Spies and Commandos, for maximum effect. Use the Spies' bribe ability to get enemy units distracted, then send your Terrorists in to bomb key sites, like National Projects or Wonders.
Terrorism is considered to be the systematic use of violence and/or intimidation to achieve political objectives, while disguised as a civilian non-combatant. One who uses terroristic tactics to coerce behavior in another person or group is generally considered to fall under the definition of the term "terrorist".
The word 'terrorism' entered into European languages in the wake of the French revolution of 1789. In the early revolutionary years, it was largely by violence that governments in Paris tried to impose their radical new order on a reluctant citizenry. As a result, the first meaning of the word 'terrorism', as recorded by the Académie Française in 1798, was 'system or rule of terror'. This serves as a healthy reminder that terror is often at its bloodiest when used by dictatorial governments against their own citizens.
In the wake of the fall of the First French Republic, its poitical ideals of social emancipation and revolution soon inspired new political movements that were willing to use any means, including violence, to achieve political supremacy. The most common perpetrators of terrorism in Europe, as it is even in our time, was non-governmental groups, especially Anarchists. One such group - the small band of Russian revolutionaries of 'Narodnaya Volya' (the people's will) in 1878-81 - used the word 'terrorist' proudly. They developed certain ideas that were to become the hallmark of subsequent terrorism in many countries. They believed in the targeted killing of the 'leaders of oppression'; they were convinced that the developing technologies of the age - symbolized by bombs and bullets - enabled them to strike directly and discriminately.
- Roberts A, BBC Home, The Changing Faces of Terrorism