when refering to many mer (or possesive such as elven) you say Meri
Meri are not from Tamriel, the beast type characters are
Aldmer are the original Meri
Chimeri are the ancestors of Dunmeri
Dwemeri inslaved the Falmeri, not the Nords, thus is why they reside in Dwemer ruins
Altmeri are the closest thing to being a pure Mer there is
Bretons are half Mer
the home continent has vanished off the face of the earth
there are sea elves with translucent skin known as the Maormer
RedGaurds lived not in Atmora, but in Yokuda which was destroyed by many natural disasters (was above the home of the Maormeri)
Morrowind, formerly known as Resdayn.  Its larger cities include: Vivec, Mournhold, Balmora, Sadrith Mora, Ald'ruhn, Blacklight, Necrom, Narsis, Tear, and Port Telvannis. ruled by King Hlaalu Helseth from the city of Mournhold
The Dunmer were once the Chimer (Changed Folk, or Changed Ones), who were a people of the Altmeri who had abandoned the ways, customs and laws of the Summerset Isles, and embarked on a great exodus to Morrowind. They followed the Veloth, who spoke to them on behalf of Boethiah, the Daedric Prince of Plots. These teachings spawned a new culture on Tamriel and a new people, even though the Chimer were physically indistinguishable from Altmer. At the time of exodus and until their change, the exiles were known as the Velothi. The term can be used in a general sense for the Dunmer as well, though it carries a specific meaning referring to ex-Ashlanders who abandoned their nomadic societies.
At the time of the Velothi's mass exodus, Morrowind was known as Dwemereth, after the enigmatic Dwemer who already inhabited the region. The exiles settled there and flourished, developing what is now known as Velothi High Culture, based on worship of the three Good Daedra and respect for the House of Troubles and the new customs. The ruins of Velothi Towers that now dot Morrowind are attributed to this period and are only common to tell-tale stories made up of legendary proportion.

Sometime around the rise of the First Empire of the Nords in Skyrim, the Velothi civilization broke down into a relatively primitive collection of clans and tribal warfare. Because of the slave revolt, many Strongholds went into opposition to hide and protect Vvardenfell's borders from the Early Nord Skirmish squads. The so-called Dunmer Strongholds of Morrowind were most likely built at this time, for defense against Nordic raiders and other Chimer too, who did not seek exile with the rest at the time of exodus. Such disunity allowed Skyrim to conquer Morrowind. The Nords ruled Morrowind, now called Resdayn, under the reign of semi-corrupt Nord Tyrants for many years, until fighting of their own (the War of Succession) allowed the Chimer and Dwemer to form an alliance against the vulnerable and rebellious Nords, and oust the occupiers.

Azura's Curse and the Chimer's Transformation
This was the era of the First Council, when the modern Great House system was in productions form but already developing, with Indoril Nerevar Moon-and-Star and his three advisors (the Tribunal ; Almsivi) at the fore. This included Almalexia, Vivec the warrior-poet, and Sotha Sil. As every student of eastern history knows, the union did not last long. After a supposed summoning of Azura at Red Mountain, where the Dwemer and Chimer fought the last of the opposing forces, Azura laid her curse upon the already-exiled Chimer. The supposed murder of Indoril Nerevar Moon-and-Star by the summoning ritual made by the Tribunal, Azura appeared, with Indoril dead, and her words hissed: ' May the eyes of the Changed Ones be turned as red as this volcanic ash, and may their skin be as blackened as their hearts. The accursed drawn, blood from the master spilled, and a curse shown in the race of these folk, forever-more'. This led to the hiding of Vivec in the Ministry of Truth and the recession of the cultures of the now accursed Chimer. Azura withdrew from the mountain, and there upon the now-Dunmer lay with ashen souls, and would reflect change in the Eras to come.

Migration - Red Mountain eruption
After the eruption of Red Mountain, many Dunmer fled to Skyrim as refugees.  Many eventually settled on the island of Solstheim, which was given to them by the High King of Skyrim at the time. A few took up residence at The College of Winterhold, but many more fled to Windhelm, the seat of the Stormcloaks resistance against the Empire of Tamriel. Before the cataclysm that lead to the mass exodus of Dunmer, several of the faithful of Azura received visions of the eruption of Red Mountain. Setting out for Winterhold, these Dunmer built the Shrine of Azura in Skyrim.  The only remaining member of this group is Aranea Ienith. Many Dunmer are returning home to rebuild their homeland.

Culture and religion
They are grim, aloof, and reserved, keeping to themselves as much as possible. They are just as distrusting and disdainful of other races as they are to other Dark Elves. The Dunmer and their national character embrace these various connotations with enthusiastic behaviors. In the Empire, 'Dark Elf' is the common used term used by any humanoid race, but in their homeland, Morrowind, and among their Aldmeri brethren, they are known as Dunmer.
In Morrowind, the main religion is the worship of the Tribunal Temple but a large number of Dunmer also worship Daedric deities. To this day, many of them also believe in Ancestor Worship. They see Mephala, Azura, Boethia as primary Daedric deities. The commoners ban their behaviors with harsh distrust. Gods worshiped by the Dunmer folk of Morrowind include:

Almalexia
Azura
Boethiah
Lorkhan
Malacath
Mehrunes Dagon
Mephala
Molag Bal
Nerevar
Vivec
Sotha Sil
Sheogorath