Atnium

Atnium, or 'Elder City', is a safe-haven for Mer of all kinds, and is also the capital city of the Eltmer. It is a hidden island in-between Tamriel and the Summerset Isles, concealed by a very similar mist to the ones that surround Pynandonea.

The High Priest of the Eltmer is the ruler of this island kingdom.

Founding
In 1E 2300, an Eltmer explorer by the name of Alir discovered this island, after forcing his way to the island using magic. The natives, which seemed to be Elf-like men, forced him out.

He fled back to the Eltmer kingdom of Artaeum, where he informed the High Priest of this land.

This Eltmer Ruler, renowned as the most vicious and cruel of this era, immediately saw the uses of this land. He sent out expeditionary forces to the island, where the armies destroyed and enslaved the native people.

Within a few years, the Royal Architect had founded a city, which he dubbed, 'Atnium.'

History
After its founding, the city of Atnium grew into a beautiful kingdom, which the Elves of Tamriel would call the 'Jewel of the Sea.'

This city eventually became the Capital of the Eltmer, just before the disappearance of Artaeum.

After many long years of servitude, the native people revolted, attacking their Elven Masters. They used boats to flee into the sea, where they formed their own island kingdom, a bit away.

The native people began the Raiding of Atnium, which lasted for hundreds of years. The native people would slide into the waterways of Atnium silently, and burn the city, in revenge.

The Eltmer eventually forsook their Oath of Peace, and retaliated, attacking the raiders and destroying them with their superior magic.

When the Reman Dynasty attacked the Dunmer, the Eltmer appeared to help. They participated in no battles, but they invited the few Dunmer who were willing to come to Atnium.

Thus, the Era of the Grey began.

The Dunmer People were not used to this calm, ocean life among the beautiful trees and plants of Atnium, and grew unsettled.

A few Dunmer decided to try to form their own volcano, in the middle of the City.

They ventured into the caves beneath the Island, and began to pray to Mephala, Boethia, and, surprisingly, Mehrunes Dagon.

The following explosion devastated Atnium, killing hundreds of Eltmer and Dunmer, and sinking the part of the Island that had been donated to the Dunmer. The Eltmer were enraged by the destruction of their beautiful island, and drove the Dunmer from their home.

The Eltmer slowly began the process of rebuilding their home.

The Dunmer who had fled back to Morrowind spread the ruin of this kingdom to the other Mer, who became intrigued.

Groups of Altmer, Bosmer, Orsimer, Maormer, and Dunmer slowly began to head towards Atnium, helping the Eltmer rebuild the beautiful island.

Eventually, the Eltmer allowed the other races to settle there, and the city finally became a city for Elves.

In the Fourth Era, the United City of Mer fought back an invasion b the Thalmor.

Trivia

 * The Current Leader of Atnium is actually of a mixed race, being half Dunmer and half Eltmer.