Well in my opinion, Deren isn't like any other country in Arunia. We've got Valond, Ildis and Adeshia, but we haven't seen the other countries of Arunia yet. So, in my opinion (even though it isn't or may be possibly canon), here's a peek on what it looks like:
1. Its cities will look 1920s-ish or something. Probably its cities will look like New York, Paris, Los Angeles, San Francisco, Manila, London, Shanghai, Hong Kong, Tokyo, Barcelona, Chicago, Vancouver, etc. in the 1920s. Or it should be something like Republic City from The Legend of Korra: vignette2.wikia.nocookie.net/a…
2. Deren will be the only "modern" country in Arunia due to its advancements in science and technology. Something like Japan.
Side note: Japan would make a good IRL equivalent for Deren
3. Deren won't have horses or any draft animals to drive vehicles, since it's way too old-fashioned. Instead, Deren will have modern methods of transportation such as automobiles, motorcycles, airships, trains, cable cars, etc. Plus, Deren has its own railway system, similar to Japan and the USA.
4. Unlike the other countries of Arunia, Deren utilizes steam and electricity effectively. Some modern-day features can be found there.
5. However, it's mentioned that Deren has lots of inventions and hosts an event called "Les Esprits Brillants" every three years where inventors all around the world go to Deren to show off their inventions. The best invention gets a prize.
6. Deren has an air force and their airships may look like this: www.airpowerworld.info/ww2-fig…
If you have any ideas, concepts, or suggestions what Deren would be or look like, please comment. Thanks!
Disclaimer: I do NOT own Deren! Well, this is fanmade
, duh! Plus, Ascension belongs to Rinmaru
. Or semi-canon. Dunno.