Update 21.11.14

Thank you very much! <3

This is a messy situation. Annexing another country without going to war (as you propose for Begus) is extremely difficult because each country has its own unique institutions that run the country. Those institutions don't disappear just because Ryen becomes king, and they are very difficult to replace. Unique peoples have their own preferred ways of doing things, and the people who hold power in a country will resist having it taken from them. Sometimes compromises can be reached, but usually not much further than values align. So Ryen would have two options: he can either leave those institutions intact and just rule two kingdoms essentially separately, while slowly pushing reforms and uniting those institutions over several hundred years, or he can violently suppress and replace those institutions. In Dorgania, Ryen will be pursuing the latter policy, and this will be relatively easy because the revolution is going to destroy much of that country's powerful oligarchy, at which point he can simply sweep in and install Central's institutions with nobody strong enough to resist him.

After Dorgania, Amagal would probably be the easiest to integrate; since Amagalites mostly care about studying magic, as long as Ryen left the universities intact, he could probably do just about whatever he wanted, especially if he fixed the famine and other economic problems, which would buy him a great deal of goodwill. The hard part is actually taking over. Varea, the Earl, and the King are all strong-willed; regardless of who is in power, they would need to be deposed, which can probably only be done in a war. This war would be relatively easy: Amagal has a very large army for its size because many who couldn't make it on their own have joined it, but these people don't really want to be soldiers, are demoralized, and would not resist an invasion particularly fiercely. Still, war is costly under any circumstances, and it would be a lot of effort to expend on such a small, poor country, especially when Ryen can depend on Varea to be generally cooperative anyway. This is especially true because Varea doesn't appear to have any particular administrative savvy and neither does anyone else in Amagal, so she might need the help of Ryen's advisors and resources to get anything done, especially until the country gets back on its feet, and that could provide him the leverage he wants anyway. Of course, none of that doesn't stop him from invading for the sake of glorious conquest, but with the Titans bound to appear at any moment, it might be wise not to bother.

Begus would actually be really difficult to unite or integrate peacefully. Jeanne would not cease to be the queen of Begus simply because she married Ryen. Legally, she is still the monarch. Of course, Jeanne is a weak, naive ruler, and if Ryen wanted to just dictate policy to her, he probably could. (This is actually the scenario I believe is most probable.) The problem is that Begus has a powerful church that would fiercely oppose Ryen, who has publicly and repeatedly claimed to be an atheist whose primary concern regarding the church is that it not be politically powerful enough to oppose him. You think the church stonewalls Jeanne's every move, just wait until they are faced with an actual ideological enemy. I imagine they wouldn't even tolerate him marrying Jeanne in the first place and instead try to depose her. Without weakening the Church considerably, Ryen probably has no diplomatic way of influencing Jeanne much more directly than he already does (e.g., via closed-door meetings with her). And destroying a church violently is nigh-impossible while that religion continues to enjoy popular support, so that's not an option either.