Thalthil Dres was the Grandmaster of the Great House Dres during the first era. It was because of his leadership, House Dres was elevated to the status of Great House after a very successful slave revolt in Black Marsh.
Thalthil Dres was the Grandmaster of House Dres, an insignificant house in the province of Morrowind. The Dark Elves of House Dres were experts in the ways of agriculture, establishing saltrice fields as far as the eye can see. Not to mention being proficient in the slave trade. But Thalthil would give House Dres their big break with the Raid of Thorn, which was an attack on the Black Marsh city-state of Thorn, located just south of Tear, where House Dres would normally operate. Thalthil advanced onto the city-state of Thorn and initiated a slave-raid, capturing various Argonians for their plantations. The raid on Thorn goes down in infamy as a violent and heart-breaking event in Tamriel, but regardless, House Dres would rise above the ranks and become established as a Great House.[UL 1]
Thalthil Dres established the slave trade as it has appeared throughout the eras, eventually incorporating the Khajiits of Elsweyr and other races that were unlucky to encounter the Dres. Eventually, the Great House Telvanni had begun to take in slaves as House Dres began to bring them onto Morrowind. However, the Raid of Thorn had created a growing vengeance from the people of Tamriel, especially the slaves. Various slave outbreaks occurred throughout the eras, such as the Raid on Tear and the Arnesian War. Eventually, when the Dark Elves were weak and the Argonians grew stronger, the Accession War had arrived onto Morrowind, besieging various cities including Tear and the House Telvanni cities. The Slave Trade had proved to be the downfall of Morrowind during the Fourth Era, with the Accession War. It is unknown whether the practice of slavery continued in Morrowind.
- The Elder Scrolls Online (mentioned only)