The actual origins of the Mercurian peoples are shrouded in mystery directly as a result of how we lorified the creation of the server way back in 2010. Here's the 5-minute version:

Hermertia actually began in 2010 as a 'survivial island' world for a group of friends (Regent, Kyn and Scrios, etc) to play and LAN party on. That island, as you can see from the above map of the Old World (just south of Channoria), was Mercury Isle. As the server slowly attracted interest from the outside world, player unaffiliated with that original group began to join. I, along with Sam and Gimpy and a few others, joined in 2013 well after Hermertia had been truly established as a lore-based rpg world.
That first group wrote much of the only half-history, half-mythos that we have about the time before the first settlers landed on Mercury Isle. That information was housed within the Old Imperial Library, and has been restored by our intrepid scholars
here.
Gameplay began in the Cycle of the Owl; all events before that are considered historical in that they were not derived from in-game actions but written as lore to explain the origins of our world. It seems that no one will ever truly know what occurred at the dawn of time, but the first widespread race we know anything much about are the elves - this race was populated by multiple species, most of whom survive today with varying degrees of prominence and activity and have played important roles over the course of our history in both the Old and New Worlds. The elves grew into a vast empire, but sought greater riches: their genetic experimentations on early humans created the orcs, a chaotic species that played an important role in Old World war and politics but did not venture to the New World.Other species at the time include the dwarves: a much more mysterious race and one rarely heard from, with the rare exception.
But I'm getting off topic. After the trials of the Cycle of the Moon, humans gained power for the first time and established the Empire of Man. From what very little we know and have passed down over aeons, the Empire as a precursor to our own was a cruel and chaotic one; it subsumed other cultures, often by force, and led to bickering and infighting amongst lords and nobles. After an indeterminate time, a blight we know almost nothing of but that scattered references have referred to as The Strife began to spread through the Empire; communication collapsed and chaos reigned as disasters both natural (great storms) and mythological (great serpents rising from the seas) overtook the Empire. The people began fleeing to the very outer edges of the Empire; one colonisation ship sailed past the extreme edges of the known world. Generations later that ship would run aground on Mercury Isle, and the descendants of the last ship of the old Empire would name themselves the Mercurians. This brings us full circle.
So to answer your questions:
- The Mercurians are the ancient descendants of the Empire of Man; they originally formed the Old Kingdoms but are now so spread out among the reams of Hermertia, so intermixed, that they are no longer of a particular culture or Kingdom. The overall ethnic composition of realms varies dramatically: Wysteria holds Mercurians, Ertians, Marseeans, etc, while a realms such as Dawnstar is heavily populated by snow elves.
- We don't really have an analogous nobility system in the way you describe it; Mercurians are both nobles and serfs in Hermertia. Unless I'm just misunderstanding your question, aha.
- So to say that Mark Stefan was Valyrian and Mercurian would be correct, for sure.
Hope this helps! Some great questions here that really encourage us to go back and take a look at our history
