So, here my idea on the religions of the three dragons:
The cult of fire dragon/ Ice dragon/ Wind dragon (I'm not sure for the last one because It's hard to read on the screen
)
These three cult are very ancient religions, who worshiped ancient dragons who, a long time ago, ruled the tribes of mans in the regions, before the rises of Nohrian and Hoshidian peoples. They will have the pagan attrition bonus (because they live in very hard places) and it will be difficult for them to convert a provinces. But the three of them will own a religious leader("keeper of the flames", "Wizard of the winter", and "Winds Whisperer" for example) , but they will have to show is strength in the rite of the fire/ rites of the Ice/ rites of the Wind, it will be a chain of events, where he will have to face the wild, and if he succeed (but it can cost his life) he will become the religious leader of his religion and give to his cult a strong bonus of authority, and he will have some others bonus. But if he fail in his quest, the religious leader's title will be destroy, and he will have a great malus in piety and prestige (if he doesn't die in the quest). So, it will be hard to keep the religious head in the times. But there is a possibility to reform these three cult.
Two possibility for that, the first one, the more "simple" will be to earn three of the holy site of the faith (the three religions shares the same holy site because they have the same origins) and reform like others religions, you will create the "Church of the three headed Dragon", who is an unified form of the three religions, who will became heresy of the Church. But the others possibility will be, for one of the religious leader of the three cult, to take the path of the reunification, it will be a chain of event for a very pious and prestigious rulers, who can decide to travel to the two others tribes, and try to convinces them to joined an union of the three tribes, in one kingdom and one religion. But it will be hard to convinces them, and he will have to show his strength and his bravery.
The Church of the three headed Dragon" will have a more stable religious head, but a ruler can always decide to take the path of the first prophet who unified the three cult, with all this difficulties.
And that's all for today, I will probably wrote some thinks for the Monsters of Magvel and the situation of Ferox tomorrow