This server is a nation called Grand Empire and it is based on feudal Japan. It is on an SMP called Ruby and it does not use mods.
The Empire is all about discipline and hierarchy and imperial order. You join one of the legions and serve in your own way. There are Imperial Guards that protect the Emperor and keep the laws. There is the Royal Legion that is like the elite force. There is the Iron Legion that is the main army of the Empire.
The legions are all recruiting right now because this nation is new. That means it is easier to get in and rank up. If you join early you have a better chance to rise through the ranks and earn respect.
You can build bases and castles and settlements that match the style of your legion. There is a rank structure so you can progress by helping the Empire. Players do missions and ceremonies and live in an organized Empire style.
If you want a more serious nation roleplay with legions and an Emperor and no mods this server really fits that vibe.
