[quote=@Zeroth]
Just to confirm, this is an alternate world---when you say the DUA is "resemblant" of the USA, you just mean that they're similar, and this is NOT a fictional future-Earth at all but a separate, distinct Earth-like planet?
[/quote]

Correct! 💯

The DUA was a continental power, as stated with multiple nations that made it up - the original Republic of Sevara being one of several. (The exact number is still up for consideration but will be give or take around ten.) Sevara specifically is based heavily off RL Colorado in context of geography, climate, flora and fauna, and etcetera. (Just to add.)

[quote]
The "enigmatic Arcanii" made me think of the word "arcane," so will this RP feature any sort of magic or non-scientific, supernatural force? Or will it stick more to the realm of science-based, technological "powers" and firearm based weaponry?
[/quote]

This RP will strictly be science fiction with zero “magic”/arcane influence. I will say though on that that things will be quite diversified. Along with conventional “slug throwers” there will be laser-based weaponry as well resources such as drones, power armor, explosives of varied effects, varieties of melee weapons, useful applicable serums, cybernetics… etcetera. 

[quote]
What are the nature of the mentioned mutations? Bestial mutants are mentioned, so I'm sure those are environmental fauna/flora threats, "monsters" in JRPG terms, but do mutations also affect playable races/people? If so, how does it change their appearance, combat abilities, etc?
[/quote]

Unlike a lot of media that have “categorized” such the approach I am taking with this RP is that the mutations, be they radiation induced or lab engineered, are “endless” - for lack of a better word - in variety. Mind you I am not going to take, nor allow, a completely ridiculous avenue when it comes to this. Each mutant be it human (oid) or animalistic in nature is unique. In some cases such as a gigantic mutated ant queen there are very likely be others such as it but this is not a guarantee. At least not locally. A human meanwhile that was subject zero for a specially designed mutagen agent that was deemed as a failure - and said human was “discarded” but survived the apocalypse - is likely the “only one”. 

Does this make sense?