#darkphoenixdragon

Language gets so complicated so fast and in general I tend to gloss over it through use of a ‘common tongue’ because I have other things I’m more interested in tackling than overcoming language barriers.  I actually made a post on the art blog a while back that talked specifically about language and its diversity through the Awakening world, but specifically for Twist of Fate, I think there are some interesting points that we can make: 

Because Plegia’s people tend to be so scattered, there are a lot of different Plegian dialects around.  In general, though, they can all understand one another well enough, barring regional colloquialisms.  Depending on where they are, some Plegians might only know their native tongue and nothing else, if they don’t interact with other groups; but villages closer to borders tend to have a fair understanding of the continental common language, plus a scattering of either Feroxi- or Ylissean-specific skills; coastal towns are less likely to have the continental common language, but significantly more likely to be versed in Valmese language groups like Rosannois, Chon’sinese, etc. due to ocean-based trade. 

Robin is versed in several specific languages, among them Ylissean, Feroxi, Rosannois, Chon’sinese, and at least a handful of Valmese dialects common to traders; of these, though, he’s only fluent in Plegian Feroxi and Ylissean (plus the continental common tongue).  His Ylissean tends to be extremely formal since it’s all based on book study and diplomatic instruction, due to the tensions between their nations, but his Feroxi is more laid-back since he’s had dealings with them in the past and is on quite good terms with Basilio (who may or may not have taught him several vulgar phrases and curse words, because really, this is Basilio). 

Henry and Tharja, as Robin’s bodyguards, have also received instruction into other languages, though they’re not fluent in anything beyond their native Plegian tongue and the continental common language: they’re primarily versed in Ylissean and Feroxi, and they can pick out just enough to understand a few languages from the Valmese continent.  

Henry 100% abuses his linguistic skills to make bad puns in class.  Also in public. 

Chrom knows Ylissean and the continental common tongue, plus a little Feroxi (which comes as something of a surprise when they go to Ferox and he can understand Basilio).  He doesn’t know a word of Plegian at the outset, which Tharja in particular abuses to have private conversations with Robin and Henry while Chrom is with them; Robin disapproves of this rudeness and will answer in the common tongue so that Chrom isn’t excluded. 

Much to Tharja’s surprise, Chrom readily picks up on Plegian as they spend time in the capital.  Book learning was never his strong suit in the first place, but being in a place that doesn’t speak anything but Plegian means that he’s picking up on context cues and learning through immersive exposure: she’s going to try talking over his head at some point and he’s going to call her out (possibly in Plegian), and Robin is not going to be able to stop laughing. 

I know there’s no time travel in Twist of Fate, but I felt like drawing Lucina and making something for this AU, so here’s a Twist of Fate Lucina!

I'm so glad you're enjoying it so far! And OH THESE ARE VERY GOOD QUESTIONS

So to start: your first assumption is 100% correct. Pretty much EVERY Plegian knows Naga's Mark, and equally know that it is Bad News (to the point that it's called the Brand of Despair on their side of the border). Robin is no exception to this -- in fact, given his upbringing and education, he's more keenly aware of what the mark entails than most, since he recognizes the political ramifications of Chrom's presence as a Branded Ylissean in Plegia.

As for how much they can piece together, the answer is 'quite a lot' -- they just keep quiet about it. This is the effective thought process Robin runs through when they find Chrom in the first place:

He may not know everything about how things work in Ylisse, but he does know that it's ruled by Naga's Branded, and the reigning Exalt has three children: two daughters and one son. Logically, then, that means Chrom is either the known prince of Ylisse or a bastard child of the Exalt.

On the one hand, he could be here on a peaceful mission, with the intention of relaying peace terms; however, this is unlikely given that no word was sent from the border of a dignitary's arrival, meaning he came by stealthy means and took pains to avoid the border guard.

If he's not on a mission of peace, odds are good that he's on a mission of war; if he is a bastard, it's possible he's trying to secure his place in the line of succession by weakening Plegia, most likely by assassinating one of the key figures in their nation (the king, the hierophant, or the Heart).

The fact that he's carrying a divine weapon means that he's doing this with the Exalt's blessing, though, which makes him significantly more dangerous.

After seeing Chrom fight, Robin's almost certain that they're dealing with the actual prince of Ylisse rather than a bastard (those sword skills don't lie), which is actually riskier because it means that either the Exalt sent Chrom on this mission personally, or Chrom struck out on his own with Ylisse's divine weapon, and either way the Exalt is almost certainly going to want his son (and his sword) back.