Thalmor

The Thalmor is the governmental representation of the Third Aldmeri Dominion, the union of Valenwood, the Summerset Isles and the client states of Elsweyr. As explained by Delphine, the members of the Thalmor are "elven supremacists" who seek to end the Empire and eradicate the worship of Talos. They claim sole responsibility for closing the Oblivion Gates in the Dominion (much like the An-Xileel), although this is partly true, Martin Septim was the one who definitely ended the Oblivion Crisis by destroying the Amulet of Kings and invoking the avatar of Akatosh.

Vahl Aradur
Vahl, after doing much of the Stormcloak quests, now attacks and kills thalmor on sight.

Origins and early history
Thalmor was the name of the provisional government set up by the Bosmer and the Altmer during the Second Aldmeri Dominion.Claiming the Summerset Isles for themselves, they renamed them Alinor in the Fourth Era. The Thalmor sought to unify the land, even before, along with parts of Hammerfell, to align it against seafaring threats that plagued the isles for centuries. The endeavor was thwarted by Tiber Septim and the "Brass God" of Dwemer origin. This sparked a deep-seated hatred for the Septim Dynasty and the man who apothesised into the deity, Talos.

The Oblivion Crisis and Fourth Era

 * "They say syndicates of wizards have led a boycott of Imperial goods, in the land of the Altmer."
 * ―A rumor

Before the Oblivion Crisis, the Altmer organization that would become the Thalmor were little more than a loud mouthed fringe group mocked openly by Altmeri society. In the waning years of the Third Era, they led numerous boycotts of Imperial goods.

When the Oblivion gates began opening all over Tamriel the Summerset Isles were thrown into anarchy. Refugees were slaughtered by the thousands. Those who tried to flee by boat found the Daedra had conjured storms to prevent escape and were cut down on the wharves and docks. Many were forced into the raging sea and drowned. Towards the end of what would become forever known as, "The Oblivion Crisis", only the legendary Crystal Tower of the High Elves stood fast against the Daedric hordes. It was there they made their last stand, in the ensuing battle the Altmer Sorcerers and Archers killed so many Daedra that they scaled the walls over mounds of their own dead. It was not enough however, and the Crystal Tower fell, literally torn asunder by Daedric machines. In those final moments, the hordes of Daedra vanished completely.

Though many disputed the Thalmor's miraculous claims, one by one they had their reputations ruined by Thalmor perpetuated rumors and were exiled. Those who continued, even in exile were often assassinated. One such famous example was the great seer-mage Rynandor the Bold. He had commanded the defense of the Crystal Tower, and was considered a great hero of the Oblivion Crisis.

Rynandor was quickly assassinated aboard a ship bound for Anvil thereafter.

Potentate Ocato's murder began the Stormcrown Interregnum. The Elder Council fractured, leading into seven years of ruthless in-fighting, plots and backstabbing. With the Empire submerged in this mayhem, the Thalmor wer

the Great War
The Thalmor initiated the Great War against Cyrodiil during the reign of Titus Mede II, seeing the frailty of the ruling class and the office of Emperor, after the Elder Council had struggled for decades to place rulers on the throne. The war was vast and bloody. During riots in Bravil, the crypt of the Night Mother was destroyed along with the last Listener, Alisanne Dupre, causing discord with the Dark Brotherhood and slowing its operation in Tamriel significantly, as invokers of the Black Sacrament no longer had their prayers voiced to assassins through the Night Mother. Four years of rampant bloodshed forced Mede II to sign the White-Gold Concordat, which included the removal of Talos from the Pantheon of Gods; the Nine Divines reduced to Eight. Ulfric Stormcloak, a Legionnaire in the Imperial Army was imprisoned. During Ulfric's incarceration, his father was killed by the Thalmor. Facing heavy torture by First Emissary Elenwen, Ulfric was eventually released, in the hope he might stir up unrest in the region thus destabilizing the Empire further.e quick to act. They overthrew the rightful Kings and Queens of the Altmer in a violent uprising. Then the first of many pogroms descended on Summerset Isle. They slaughtered any who were not "of the blood of the Aldmer" as well as many remaining dissidents. The Thalmor never wasted an opportunity.

The newly empowered Thalmor reacquired Valenwood during the Fourth Era through a coup de'tat, and the Former Confederacy of Elsweyr, shaken by political strife, became a protectorate of the new Aldmeri Dominion. The Thalmor's ambitions would not cease there however.

Hammerfell and the Markarth Incident
At this time, the Thalmor unsuccessfully attempted to siege Hammerfell, retreating after suffering extreme losses. Busied by continuing conflicts in Cyrodiil and Hammerfell, Jarl of Windhelm, Ulfric Stormcloak was able to defeat the Breton natives occupying The Reach in what came to be known as the "Markarth Incident". Ulfric asked only one promise as payment -- agreement to uphold the worship of Talos against all else. Quickly responding to the threat in Markarth, the Thalmor gave Jarl Igmund an ultimatum -- forbid the worship of Talos or declare war against the Dominion. He forsook his promise to Stormcloak. Meanwhile, the Bretons stewed in anger at this defeat, vowing to retake the The Reach and renaming themselves the "Forsworn". After the Markarth incident, the Thalmor presence in Skyrim increased, as it sought to enforce the ramifications of the Concordat.

Role in Skyrim
The Thalmor's role in Skyrim was to ban the worship of Talos, and use the Empire as a puppet.

A lot of them were killed by Vahl, but many still roam skyrim along the rest of the Empire.

Images
http://www.skyrimtravels.com/wp-content/uploads/2013/09/thalmor.jpg

http://i.ytimg.com/vi/nFNVW3vPnqo/maxresdefault.jpg