If Una is a saint then Owen is the god who created her.
The more we read, the more it seems like this is a self-fulfilling prophecy where Owen is creating the mythology that is used to perpetuate the supremacy of Dominion.
When Owen first discovers the book, he spends 6 days with it working on his first translations and studies and on the 7th day, the book was stolen so he rested. His work literally mirrors the biblical story of God creating the world in 7 days.
Even the fact that the country is called Dominon. Supposedly, God gave man dominion over the earth. The meaning of which is often debated or even shaped to support specific convictions. Does "dominion" mean the right to control and shape the world as we see fit? Or does "dominion" mean the responsiblity to protect and care for all living creatures? This debate is reflected in the world of Dominion with Owen playing a part in constructing that mythos. Is the country Dominion, a place that all the people of the land were happy to join? Or is it a place that only exists because of colonialism where people joined against their will? We are getting glimpses that Una is not as beloved in the world as we are led to believe in the modern day. And in this story, Owen serves as the god that is literally giving Dominion (the country and the control) to Una and, by extension, Queen Yvanne.
I am sure there is going to a lot more catholic symbolism and I really excited to see how Alix Harrow plays with those themes.
Edit to add: and I forgot an important piece! The fact that legend said Una heard God’s voice telling her where the chalice was but who she really heard was Owen