The game defines a national religion (which can be difficult to change, and will not be without causing widespread disturbances) that usually alters relations over time either with your co-religionists or with countries of different religions (this is particularly true for Christians and Muslims). Unless you have solid treaties, expect these relationships to deteriorate, which will not be without causing lines of fracture and therefore wars.
On a more local level, each population has a religion, which alters its loyalty and productivity (this can vary depending on whether your leader is tolerant or not), and you will then take care to gradually convert (and with more or less difficulty, pagans being easier to convert than the so-called "Religion of the Book" populations (i.e. Christians, Muslims and Jews). To do this, you will want to build religious buildings and promote populations into the clergy.
If you sin too much on your production of Piety points, then expect heresies, which are in some ways powerful rebels, who can spread their false belief in other regions. You will then have no choice but to convert them by force and blood, with an army or particularly intransigent clergy members.
But that's not all, because there is the possibility that Crusades or a Jihad will be triggered! Indeed, the game defines 5 holy cities, 3 for Christianity (Rome, Byzantium, and Jerusalem) and 3 for Islam (Mecca, Medina, and... Jerusalem). So you have a nice point of contention there, and it's a safe bet that at some point, a crusade or a Jihad will be launched! You will then see (literally and figuratively) Crusaders landing, for example, with fleets lent by the Italian maritime republics.
As if that weren't enough, there are also the Knightly Orders in the game. These will gradually establish themselves in YOUR regions, with Chapters, and will be like a double-edged sword. On one hand, you will be happy with the increased piety in the region, as well as the detachment of knights protecting it, on the other hand, they are a bit burdensome as neighbors, monetarily speaking, because what goes into their coffers does not go into yours. It's up to you to decide whether you support them or want to limit their influence.
On the other hand, from an international point of view, seeing a heavy detachment of Templars land in the Holy Land always makes an impression. But do not think that Islam is left out, because if the first Sunni feels threatened, the Jihad is not far away!
Thus, as we can see, religions are a major element of Kingdoms both from the point of view of the daily life of your populations and from the point of view of international relations and the behavior of nations towards each other. You cannot ignore it, and ignoring the piety of your population would be a major mistake. And then, building cathedrals and great mosques, what prestige that is! Not to mention that the clergy participates in the education of your population, which grants you more Legacy points, the game's victory point unit.
Stay tuned for the next developer diary on Dynasties and Characters!
