"The fires of hell await all heathens and heretics, they must all be saved!"
-Believe or Die! trait
Christianity is a religion in the Total War series. The religion appears in all of the major Total War titles to an extent. Christian Factions exist in Rome: Total War (Rome: Total War: Barbarian Invasion only), Medieval: Total War, Medieval II: Total War, Empire: Total War, Napoleon: Total War, Total War: Shogun 2 and Total War: Attila. Christianity is mentioned in Rome: Total War and can be adopted in Shogun: Total War and Total War: Shogun 2.
Within the Total War series, Christianity appears as 3 different denominations: The Catholic Church, the Orthodox Church and the Protestant Church. The Catholic Church is the successor of the Church of Peter in Rome. The Orthodox Church is the successor to the Church of Andrew in Constantinople the early games then becoming a gross generalisation of Slavic, Greek and Russian Churches in the later games. The Protestant Church is the generalisation of all separatist post-reformation churches such as the Anglicans, Lutherans and Calvinists.
Rome: Total War[]
Christianity makes an appearance in the Barbarian Invasion expansion for Rome: Total War. Christianity is competing for religious dominance against Paganism and Zoroastrianism and is one of the largest causes for settlement unrest. Religion plays a large part in the expansion and religious tension is the largest cause for unrest and rebellions in settlements due to faction state religion differences, faction leader religion differences and even governor religion differences. Christianity is the second largest religion at the start of the game, but is the only religion certain factions can follow or building buildings for, such as the Romano-British or Berbers while other powers can adopt it as their main religion, such as the Western Roman Empire. It's important when taking any settlement that the first thing you do is knock down the existing religious building and replace it with your own Christian shrine, to convert the population and this greatly reduce unrest.
Total War: Shogun 2[]
In Total War: Shogun 2, nearly all clans begin the campaign as Shinto-Buddhist. The only faction to begin the campaign as Christian is the Otomo Clan. The only form of Christianity present is Catholicism since the Portuguese were the first Europeans to discover Japan. During the campaign, clans trigger an event allowing them to choose to build Nanban Trade Ports, thereby introducing Christianity to their lands. Should they accept, a few turns after this they are given the option to convert to Christianity.
Converting to Christianity has powerful benefits and disadvantages. The Christian chain of buildings grants larger bonuses to mastery of the arts, as well as generating wealth over time and spreading its religion more rapidly than Buddhism. Christian missionaries are also superior in some ways to Buddhist monks. Christian clans can also build Nanban Quarters which in turn allows them to construct foreign trade ships. As the Otomo, the player can recruit Portuguese Tercos and Donderbuss Cavalry as well as leasing land to nanban traders.