I haven't seen anybody post about this stuff, and we got more than a few Lore Bombs this time around, so I figured I'd make a thread! The official summary thread is here, for anyone who wants to check it out themselves.

Characters
This was the meatiest bit of the Live Letter, lore-wise - we now know the names of all those new people in the key art for expansion.

Quote Originally Posted by Bayohne View Post
Hien
The young heir to the throne of Doma, Hien is a charismatic leader beloved of his people. Together with Gosetsu and Yugiri, he spurred his countrymen to rise up against their Garlean oppressors. But when the rebellion was crushed, Lord Hien vanished without a trace...
Here's our Samurai Man, then. Further commentary from the Live Letter suggests that he and Yugiri have a "chemistry" - my money is on Hien being the "Lover Lost" of the main vocal theme. Yoshida was really playing coy about him in terms of commentary, too; they seem to be building an intentional mystery around him.

Quote Originally Posted by Bayohne View Post
Yotsuyu
The acting imperial viceroy of Doma, Yotsuyu's grace and beauty belie a heart of stone. A cruel, sadistic ruler, she harbors a deep hatred for Domans. Under the pretext of purging radical elements, she has perpetrated numerous atrocities against her own people. Yet all are the hero of their own story...
I'm very, very curious as to Yotsuyu's backstory - Doman society has clearly wronged her in some way. While the description doesn't leave me too hopeful that she'll be all that sympathetic (outright cruelty is rarely rewarded in this game), it may cast some shades of grey on the otherwise-heroic Doma. Also of note: Yotsuyu is acting Viceroy - apparently, Zenos is still the man in charge, he's just delegating.

But anyways, speaking of shades of grey...

Quote Originally Posted by Bayohne View Post
Fordola
A young soldier born and raised during the imperial occupation of Ala Mhigo, Fordola was promised the world─education, training, citizenship─in exchange for service. Scorned as traitors by their people and savages by their Garlean masters, she and others like her struggle to forge their own path in an unforgiving world.
Here's our not-so-patriotic member of the Garlean generation of Ala Mhigans. Though this doesn't seem to be the exact nature of grey that some (Theo) wanted, what with her being neither pro-Resistance nor pro-Imperial, she definitely adds a new dynamic to the story outside the mold we're presumably entering it in; indeed, Live Letter commentary notes that she and hers represent a clash in worldviews between her and the refugees.

(Incidentally, I had a bit of a pet theory that the person who turned out to be Fordola was actually the still-living Real Yda, and the "Family Torn" bit of the vocal theme referred to strife between her and Lyse; this debunks her identity as such, at the very least).

The others - Yugiri, Gosetsu, Lyse, Zenos - mostly just confirm what we already know. There was a bit of commentary for Yugiri that says she'll play a big role in the later half of the MSQ, which only makes me more curious about the order we'll be experiencing each part of the world; storytelling logic points to us ending in Gyr Abania, as that's where our Final Boss is, but now I'm wondering if we don't somehow chase Zenos back east.

Thavnair
This was an interesting tidbit from the Q&A:
Quote Originally Posted by Bayohne View Post
Q6: Will the island of Thavnair (Radz-at-Hahn) make an appearance?

A6: Travel to these locations will not be possible yet in Patch 4.0. However there are areas in preparation where you can enjoy the feeling of Thavnair, which you can visit starting in Patch 4.05 once travel is available.
What could this mean, I wonder? Surely Omega Savage (the only content confirmed for 3.05 specifically, at least as far as I recall) won't involve a different location/feel than Story Mode; is this perhaps a hint at further Aquapolis? Deep Dungeon? Perhaps even Eureka? Totally aside from getting confirmation of some sort of non-Savage content in 3.05, I'm very interested in seeing more Thavnairian flair in the game.

We also got a confirmation of a return to Job Gear from Job Quests, the implication of Au Ra children on the Steppe, and the confirmation of Tomestones as the endgame currency (which seems a bit tired, to me - surely we could use a token that has a little more local flavor - but I guess those Allagans were pretty widespread).