Barbarians are a special "civilization" that is always at war with all normal civilizations. Barbarian units can be spawned out of nothing via a random process. Players often refer to barbarians as just barbs.
The term "barbarian" was created by the Greeks; it was originally used to denote any foreigner. Since then it has gained a more negative connotation, and it is commonly applied to civilizations deemed "inferior" to one's own. The Chinese, for instance, thought of all foreign cultures - everybody from the Manchus to the Turks to the Europeans - as barbarians. Rome applied it to the Huns and the Germanic tribes, as well as to the more advanced Gauls.
In Civilization IV, the term denotes people that are not part of any organized civilization appearing in the game, but are instead old-style hunter-gatherers who prey on the "weak" civilized world. Though some barbarians may have acquired fairly advanced weaponry - swords and axes, for example - and though they may occasionally capture or even build their own cities, they remain at heart brigandic nomads, destroying everything that comes in their path. Barbarians cannot be bargained with or appeased: they must be destroyed - before they destroy you!
Barbarians can be built normally in barbarian cities. When the city has enough defenders (the number varies with difficulty level), extra units will leave the city and wander the continent.
Barbarians can also be generated out of nothing, in any land or coast tile which is
- out of the line of sight of all cities (including barbarian cities),
- out of the line of sight of all units (excluding barbarians), and
- not within the 5x5 square centered on any existing unit (excluding other barbarians?).
The chance for barbarian generation is higher for tundra and desert tiles. In the very early game, the barbarians spawned will be animals. After a particular turn, animals can no longer spawn, and only normal units (Warriors and Archers initially) will spawn.
One other way in which barbs can be created is via events. There is a rare event called "barbarian uprising" which can happen very early in the game, producing a stack of barbarians that will invade and attempt to take a city.
Barbarians can never be permanently wiped from the planet. Even if you destroy every barbarian unit and city currently visible, they will always respawn eventually.
A number of special rules apply to barbarian units. Both human and AI players are given bonuses in combat against them, even including "free wins" for humans at low difficulty levels. However, the amount of experience a unit may get from fighting barbarians is capped. A unit cannot raise its experience above 5 experience via fighting animals or above 10 fighting other barbarians.
Here is a table relating the difficulty level to various aspects of barbarian units:
The barbarian civilization is a civilization that is always at war with other civs, and cannot communicate with them. It is led by a leader with no traits (modeled after Sid Meier, though cannot be talked to in-game). Other than that, it behaves like AIs do. Barbs do research new tech (although very slowly).
Some time after the point in the game where animals stop spawning, barbarian cities can randomly appear. Barb cities follow the same limits on spawning as units do.
Barbarian cities follow the same rules as other cities. Eventually they will build Workers and improve their land. A city will build buildings if the barbs have the tech to do so; this may include culture buildings which will eventually expand the barbarian cultural borders just as civs do.
The city names come from tribes and cultures not included in the Civilization series.
List of Barbarian "Cities"Edit