Source: Census undertaken by Institute for Mar Saran Geography and Climatology, 4680 ASC
Kop'mar
Kop'mar is the oldest and most popular religion on the island. It has a rich body of folklore relating to the origins of the island. Adherents of the faith revere a triumvirate of powerful warrior-gods, called Xultan, Jacurutu and Shala. They reigned over the island and each one is associated with a particular great power, which they all shared; and each controlled an army of daemons. Xultan was able to form and reform land masses to his will and transform the flora and fauna that occupy it. He commanded the Myconids, men who grew out of the ground like mushrooms. Jacurutu was able to perform spectacular sun miracles, affecting the length of the day and the potency of its rays. He commanded the Pantherfolk, ferocious half-felines. Shala could control the rain, winds and the sea. She commanded dragons.
These three gods elevated man from his animality by giving him three competencies: that of association and empathy with his fellows, beyond base instincts seen in animals with regards to their children, just as Xultan, Jacurutu and Shala who came from different ends of the universe but loved one another as brothers and sister; that of technology, by giving him the bastardised power of Xultan to make tools from the earth, to make false night and protection during it by creating buildings as a homage to Jacurutu, and the ability to build ships to tame the wild seas which Shala could command with his mere thoughts; and above all a comprehension of the gods themselves, which animals could never have. For some, much-disputed reason, the three gods left Mar Sara. Some say because they wanted man to govern himself, either to prove his worth or (knowing we would fail) for their own sport; some nationalists have said that Shirerithians killed them. Either way, all Kop'mar look for the return of these three gods which will signal the end times, when all lands of Micras but Mar Sara will burn and all true believers will join the three gods in the stars for eternity.
Worship is led by local elders of lore, and great emphasis is placed on knowledge and understanding in Kop'mar as the unifying element behind the three gifts of the gods. There may be one elder in a small village, or several, depending entirely on their competence; and villages that adhere to Kop'mar have been known to disband entirely because of a lack of knowledge, and their residents go roving for a new elder. The religion is very localised and there is no centralised structure. There were historically three Grand Elders, one with knowledge of Shala (on the west coast), one of Xultan (on the east coast), and one of Jacurutu (north-east coast). The shrine to Shala remains, but there has not been an elder there for thousands of years. The shrine to Xultan has been impenetrable for an even longer period, because all those who approach it are seized with headaches, sickness and inevitably death (some say a sign of man's unworthiness). The shrine to Jacurutu was brought down by an army of Matbaic fanatics shortly after their total colonisation of Mar Sara. Today its adherents are spread across the island, and can be found as often in villages as large cities.
There is a distinct sect within Kop'mar, distinguished because it adds a fourth, primordial creator god, called Huub. Even within this sect there are disagreements as to his nature. Some say he was the father of the three gods, and that he granted them their powers. Others say they were his servants who betrayed him and cut out his heart, sharing it between them and eating it to gain a portion of his power. It has its own Grand Elder in Augustgrad, which Huubist lore states was his seat as true sole god-ruler over all of Mar Sara. Huubism is prevalent mainly in the south of the island, concentrated around the capital city.
Cedrism
Cedrism was brought to Mar Sara by Shirerithians and its priests and followers have dedicated much time proselytising the local Kop'mar. Their main thrust was that Xultan, Jacurutu and Shala were all gods of the Cedrist pantheon- Terra, Ra and Mo'll respectively. These are just different names for the same god; and other elements of the Kop'mar faith are incorporated in Cedrism, for example by revering Gaelen as God of technology. This movement always had very limited success but steady immigration and the evolution of a County bureaucracy that favoured Cedrists over Kop'mar have led many native Sarans to convert.
The Cedrists of Mar Sara themselves differ from those of mainland Shireroth in two key respects. Firstly, an idea was introduced by converts from the Kop'mar that Gaelen did not quite capture the essence of the gifts offered by those gods, and since a dialogue was opened, eventually the Cult of Zahnrad, God of Tools, was established and recognised in Mar Sara. A great shrine to Zahnrad competes with the preachings of the Grand Elder of Huub in Augustgrad. Secondly, a particular aspect of modern Cedrist philosophy is missing; or rather, a widespread mistake or misconception, once corrected, was never corrected in Mar Sara. This occured during the second wave of Shirerithian immigration after 3200 ASC, a colonisation of the north that went awry after the Landsraad withdrew approval. Alongside these events, the Rahikkalan Rejection was taking place. Eminent priests and philosophers debated core tenets of Cedrist belief with regard to the 'Immoti', and it was eventually agreed that it was a misunderstanding of the prophesies. Now, those adventurers who eventually settled in Mar Sara, having left before this took place, were unaware of it, and so were the priests that accompanied them; but further, they were joined by Shirerithians who fled that they perceived to be a danger of persecution for sticking to their beliefs in the Immoti. Therefore, though modern Cedrism has a place in Mar Sara, the majority of the believers still adhere to this heresy.
Cedrism is also found across the island, but primarily in the south, where the Counts have long guarded their rights and given them preference over other religious groups.
Matbaic Orthodox
Between 2499 ASC and 3181 ASC, the entire northern half of Mar Sara was controlled by Matbaa. Both in its Zatriarchate and Ecumenical Synody forms of government, that nation was a highly fanatical theocracy, where religious minorities were viewed as a 'To-Do list' (the exception being Christian minorities such as the UCS). Now, I have already mentioned before that certain RL Christians in micronations strongly object to Christianity on Micras, not I feel in a 'this-is-blasphemy-please-stop' way but more 'this-doesn't-make-sense-and-you're-talking-about-my-RL-religion-here' way. I really don't see much difficulty with having Christians on Micras but I am not really best placed to explain all of that, especially given that Matbaa is dead, and so I will just say: don't worry precisely what 'Matbaic Orthodox' is. It's an Orthodox religion, so they claim adherence to some old position. Be that Christian or not, for story purposes, the only relevant facts are that they are awaiting the return/arrival of someone holy, which applies to many religions in RL anyway. With that said, the Orthodox Church spread in the north like wildfire, primarily because where the first settlers landed, small kingdoms were established and they were eager to spread the faith by the sword. Later, after the Zatriarch's arrival and the bringing of an end to such strife, theological conversion was attempted and seemed to prove very successful. (Xultan, Jacurutu and Shala were explained as three parts of some kind of... Trinity? And there was definitely something about resurrection or return...) However, after the state failed, old practices wormed their way into the fore again. Matbaic Orthodoxy was so closely tied to the state - it was useful for many reasons, including trade, good government, etc. so people were encouraged to convert. Once those benefits went away, the Elders whose followers had waned proselytised right back and were able to restore many to the Kop'mar faith.
Matbaic Orthodoxy was highly hierarchical (check out the clergy's garments!), but post-Zatriarchate, the sole religious authority for the Diocese of Suryo was the Bishop of Suryo (see Diocese map here, note Cathedral "Mar Kyriakos" location close to New Gettysburg/Yira), who the Anticans tell us was still whipping up rebellion during their insurrection in 3400 ASC (Octavius' awesome backstory). He remains to this day the figure of religious authority for Orthodox followers (primarily, but not solely, ethnically Matbaic), who are for the most part to be found in the areas of Matbaic settlement in the far north of the island. Abbots retain virtual independence from him in the monasteries that dot the central mountains, but pay lip-service to him as possibly the only Bishop left. Though the Zatriarchal Colony of Kefr Zeh was once considered part of the Bishop of Suryo's ecclesiastic jurisdiction, no contact has been made with those colonists since Matbaa collapsed.
Bacchic Rites
The Rites were brought to Shireroth in 3569 ASC and in 3573 ASC, at the Bacchic Debate it was agreed that the Cult be limited to the boundaries of the Duchy of Yardistan. Its followers, few in number, flocked to Mar Sara because of its pluralism and protection of religious rights. The other major place of worship is the Temple of Dionysus on the island of Yardistan. The capital city of Augustgrad houses the Shrine to Bacchus Zoros, and that is the location of the majority of the Cult's followers on Mar Sara.
Atheism
Atheism was brought to Mar Sara in 3348 ASC by the Anticans, who have never been big on espousing a religion. The following story describes the first contact between Mar Sara and Anticans.
Anash groaned. The village fool was right. Usually, when Jujar said something, you ignored it or safely believed the opposite. When he said that great metal boxes had landed at the beach and blue men were unpacking a city from it, Anash had originally opted to ignore him. But Jujar kept on and on, and would not relent, so Anash- being the man of science that he was- agreed to go have a look and prove that there were no such thing as blue men or metal boxes containing them. For that matter, cities could not be unpacked. They grew, and died, like people.
However, clear as day, Anash could see hundreds, nay thousands of men in blue uniforms working on what appeared to be a city half finished. It wasn't half there, half not; this wasn't a city being built; there were huge buildings, the like of which had never been seen in this stretch of north Mar Saran coasts, fully completed, with one particularly grand-looking building even covered in winding vegetation not native to this island. Large swathes of nothing occupied the space between these buildings, while the uniformed men pottered about between them with measuring tapes. Anash knew what was going on. Another country had come to claim Mar Sara as its own, and he knew the drill well. He put the heavy, pearl-laden cross that hung around his neck on a chain underneath his cloth shirt and proceeded down the hill, with Jujar in close pursuit. After he got closer, he was able to see a road sign, in several languages unknown to him, but in the tongue of Shireroth the words: "WELCOME TO SANT MATEU! Population: Don't know yet!"
After a few minutes Anash was close enough to call out to one of the blue men. He looked up, dropped his tape measure and shouted, "First contact!" He ran up to Anash and saluted. In horribly accented Shirerithian, he declared, "Petty Officer Hart of the SS Syren!" Anash feebly returned the hand gesture and said, in even less intelligible Shirerithian, "After this sun, you to here stay?" Hart gave him a quizzical look, then addressed him in the Saran tongue. Anash learned that indeed these people in blue uniforms were here to stay, and were building ("reassembling") a great city here for their people. So Anash's natural new question was, "So what is your god?" To which Hart replied, "God? I don't have a god. I think we may have a Norse fellow aboard..." No god? Anash thought. "But who will be OUR god?" stressed the confused Mar Saran. "Whoever you want him to be, I suppose," replied Hart. Anash gave this some thought, and inquired, "Could... I be god?" Hart, tiring of these questions when he had so much measuring to do, said, "Yes, you probably are. Now please leave the Exclusion Zone, and tell your friends not to penetrate the perimeter." Dazed, then joyful, Anash explained to Jujar what had happened. Afterward, he cracked his pearl crucifix and left it lying in the dirt, and went back to the village to tell everyone he was god.