Note: This article covers a lot of real-world references and general setting rules.
Aedyran is the language of the Aedyr and is spoken in the Aedyr Empire, the Free Palatinate of Dyrwood, and the Penitential Regency of Readceras. Aedyran is derived from the now archaic dialect Hylspeak and Eld Aedyran.
Dyrwoodans have appropriated some words from Vailian(e.g. "duc").
Vailian Republics and Old Vailia speak Vailian, which borrows from a mix of Italian, Occitan, Catalan, and French roots, but is Italian in overall flavor. "Romance-y", you could say. j, y, and x are extremely rare in their words and names.
Engwithan and Glanfathan
Engwithan and Glanfathan are from the same part of the world and are loosely related (as Cornish and Irish are). The ancient Engwythan language (used by the eponymous culture and nowadays extinct) is based on Cornish.
Glanfathans speak Glanfathan, which borrows elements of Cornish, Welsh, and a bit of Irish. q, u, x, y, and z are all unused in Glanfathan. w is both a consonant and a vowel ("uh" or "oo" if it has a circumflex). It has the Irish-style "si" ("shih" or "shee" when there's a circumflex over the i), the Welsh "ll" (hard to explain, like an aspirated l sound), and distinguishes between an unvoiced th (like "thought") and a voiced dh (like "the").
Huana and Rauataian
The Huana people of the Deadfire Archipelago speak the Huana language, which has gone almost entirely unchanged in the thousands of years since the original settling of the Archipelago thousands of years ago. Seeming to be based at least mostly on the Maōri language, possibly with some Japanese influence, Huana consists of thirteen consonants, five short vowels, and three long vowels. Words often use repetitive syllables, and almost always end on a short vowel. The Rauataian language also originated from Ancient Huana, but developed much differently over the millennia, taking several influences from Vailian and Eld Aedyran, which can be seen in certain Coastal Aumaua names such as Scâthden or Täog, or the name of the royal capital of Tâkowa.