Venture Though Tamriel
The Thalmor was an Altmeri government established in Valenwood to serve as their representative in the Aldmeri Dominion (circa 2E 830), a union of the Bosmer and Altmer provinces. They claimed they had the authority to create this government on behalf of a local Bosmer claimant, Camoran Anamexes. As Valenwood possessed no true government prior, the Thalmor purported to maintain order in the region to uplift their Bosmer brethren. The formation of the Thalmor was not an altruistic gesture, however: the Altmer sought to control Valenwood because the region, along with southern Hammerfell, harbored many pirate groups which threatened the shore of the Summerset Isles. The Altmer had become fed up with their long history of pirate attacks, and sought to secure the shores of Summerset by leaving those pirates no place from which to attack them. The Thalmor was dissolved a short time later when Tiber Septim brought Valenwood into his Empire using the overwhelming power of the Numidium.
Centuries later, a new incarnation of the Thalmor arose in the Summerset Isles, reportedly claiming to have saved the Altmeri people from the Oblivion Crisis. In 4E 22, the Thalmor took control of the Summerset Isles and renamed them Alinor. Valenwood was brought under the Thalmor’s control in 4E 29, recreating the Aldmeri Dominion, and later, what was once the Elsweyr Confederacy reverted back to the ancient kingdoms which had formed it, now acting as client states of the Thalmor. It is said that of all of his enemies, Titus Mede never managed to defeat the Thalmor, and it would be Titus Mede II who would pay the price. When Titus II inherited the Imperial throne, the Thalmor instigated the Great War with him by delivering a series of ultimatums to the Imperial City, then presenting the head of every one of The Blades’ agents in the Aldmeri Dominion when he refused their demands. After four years of bloody war, the Emperor was forced to sign the White-Gold Concordat, essentially giving in to their demands. One of the terms was the outlawing of the worship of Talos, and the right of the Thalmor to enforce that ban within the Empire. Another term of the Concordat was that the Empire relinquish large tracts of land in southern Hammerfell to the Dominion. Even though the Empire acquiesced, the Redguards of Hammerfell fought on and eventually repulsed the Thalmor from their territory, leading opponents to believe that the Concordat was a mistake, and Titus Mede II overestimated the Thalmor’s strength when he signed it.
Nevertheless, the Thalmor have the legal authority to root out and persecute Talos worshippers. They carry out campaigns to do so from their embassies in the various provinces, which also allows them to gather extensive information on the Empire’s internal affairs. It’s widely known that they see men as inferior and themselves as the rightful rulers of Tamriel, and it’s believed that it is only a matter of time before they seek to act on that belief again.