Hi!! I wanted to ask about the RCU and the sorta mixing of cultures, overlap, and the pigin language from the wither rose trade language (I feel like Im mangling that word-)
hi!! sorry it took a few days for me to answer your question, i got sick irl
so i feel like this question is specifically focused on the Wither Rose Alliance kingdoms? (if i'm mistaken my bad lmao) so i'm going to answer based on those 4--being Mythland, the Grimlands, and the Crystal Cliffs as the 3 founding members, and then Smallhold as the most recent official addition.
all 4 kingdoms have their own distinct cultures, and describing them all in detail would require 4 separate posts, so i'll give a basic summary here.
The Grimlands: technologically advanced, with a strong cultural focus on the sciences, logic, and reason. they are very stoic and tend not to show emotion often. highly anti-magic; they see magic as unpredictable and irrational. highly progressive, with technological innovations coming down the pipeline often.
The Crystal Cliffs: magically advanced, with a strong cultural tie to arcane magic in particular (as opposed to nature magic). they prioritize learning, accumulating knowledge, and gaining wisdom. they think the Grimlands' views on magic are stupid, but their allyship is so close that they graciously look the other way.
Mythland: HUGE, very rich, and very powerful. large divide between the wealthy upper class and the poor lower class. massive trade nexus. rich, deep cultural/religious beliefs involving blood, most rituals require blood to be spilled (usually by pricking a thumb or palm).
Smallhold: small, as the name would suggest, but powerful in trade because they are a food-producing breadbasket. one of the few nations to democratically elect a ruler. deeply tied to the earth, nature magic, seasons, the harvest, etc. and have a strong cultural focus on protecting, nurturing, and attending to the land.
now obviously some of these cultural elements--for example the Grimlands' distaste for magic and the Cliffs' love of it--can't really overlap. however, lots of things do, especially in the empires that are nearest each other. common languages, for one--the Grimlands/Cliffs both speak Grimmish as a mother tongue, while Mythland/Smallhold both speak Mythik. there are also common regional folktales, common popular historical figures, etc., as well as the Wither Rose Alliance Festival, which is hosted each summer in Mythland and celebrates the creation of the alliance around 700 years ago. entertainers, speakers, and guests from every kingdom come to this, and it's where you'll see the most cultural mixing.
Wither-Common is also a uniting factor, and in some regions (especially merchant-heavy ones) it's actually spoken more often than Grimmish or Mythik. it is a pidgin language, created for trade, and borrows grammar and vocabulary from both Mythik and Grimmish, so speakers of both can usually understand it okay. as most pidgins do, it started out very simple and sparse, but evolved over time into a vibrant and flourishing language of its own.
i hope this answered your question! :]