There are currently 24 factions in the game; each one based on a historical mediaeval civilisation. Players of the CtW however may also meet sub-factions and barbarians, which may be based on one or more civilisations, and even field their own special units and styles of play.

Each faction has a constellation of unique units, national powers, and religious- and culture-related bonuses which give it a variety of strengths and weaknesses. It is up to the player to decide what units to build and what technologies to research in order to create an army to best his or her opponent.