Barbarian Invasion is an expansion for Rome which takes the action forward to the period of the decline of the Western Roman Empire. It begins in 363 A.D. and ends in 476 A.D. The expansion includes simulation of the religious tension of the period. The Western Roman Empire: Playable. Although large and apparently highly advanced, the Western Empire by this stage is weak but the Eastern Roman Empire: Playable is the richest faction in the game, the Eastern Empire's army is a mixture of Eastern-style cavalry and Roman infantry (which, like the Western counterpart, is inferior to that of the earlier period).
Romano-British: Non-playable. Culturally speaking, a Roman faction. They appear when the Western Roman Empire loses their British provinces. The Romano-British primarily use renamed Roman units such as "British Legionaries" This is seen in the Movie King Arthur.