Pre Note: This is a theory, and I took info off of the QnA, ingame, and what vetex has said before about the story.
In the QnA, when asked what their favorite part of the Nimbus Sea Story was, they said:
This means we’ll see someone very powerful, who we might fight later in the story, and
I have a good Idea on who I think this is, based off of a lot of Ideas.
Some people think it’s going to be Wotan, which isn’t a bad idea given the current information game, but I feel that The Crown Prince of Thorns fits the role description better. If you think about the lore behind him, he was the person who “ruled an unknown domain on the other side of the Seven Seas” (probably the war seas), and also IS cannon in the story, as mentioned in the journal from Blasted Rock.
The story makes sense as well. He has the steel curse, making him a powerful threat, along with having at least one general with a curse (Avery Walker with the slash curse). He could also be an option as an Order of Asier high lord, with Avery walker and one of the “other leaders” that Maya mentions as Barons.
Given how far south the nation is, it would make sense that we would meet the Apex early, see them in most seas (or every sea past The Bronze Sea). He also seems like a guy who wouldn’t be messed with, given how in WoM lore he discovered the contient.
My final reason is that they said they couldn’t reveal the World of Magic ending until Ao ended, because it was similar. I’m no expert, but I don’t think Wotan and his sons were terrorizing Magius, but John Thorne the Prince of Thorns WAS around in World of magic, which makes an ending involving him realistic as an ending possibility for both, considering he was the discoverer of Magius in World of Magic lore, and he might be the “Apex of Power” in World of Magic.
I think that John Thorne has to at least be a decently large part of the story, given him being a re-occuring character from ALL 3 games, (he retired in the 6th sea of AA)it seems like they definitely had plans for him. This theory may have just evolved from my love for the Thorne Empire, but I think that The Crown Prince of Thorns is the Apex of power. but lets be honest, the real Apex of the world was the friends we made along the way.
Edit: The addition to Blasted Rock mentioned in the QnA might also be something Related to the Thorne Empire. (Thorne Empire vs Ravvenna was the battle of Cassia town.)