Thot Gor was a high-ranking Breen officer in the 24th century Breen Confederacy. He became known for beginning the relationship between the Confederacy and the Dominion, signing the Breen-Dominion Alliance.
Gor became a thot by 2375. He was approached in mid-2375 by the Female Changeling for an alliance between the Dominion and the Breen, as the Dominion War, fought between the Dominion and the Federation Alliance in the Alpha Quadrant, grew to a stalemate. After several subspace communications, Gor agreed to the proposed alliance and served as the Confederacy's first representative to the Dominion, foreseeing an opportunity for conquest as a share of the defeated Federation Alliance. Gor traveled to Cardassia Prime to sign the treaty between their governments. En route, his ship captured Lieutenant Commander Worf and Lieutenant Ezri Dax, who had been stranded on a planet in the Goralis system. Gor decided to bring them as a gift to the Dominion when he boarded Weyoun 7's attack ship to meet Weyoun, Damar, and the Female Changeling. (DS9: "Penumbra", "'Til Death Do Us Part")
With the addition of the Breen forces, the balance of power in the war was shifted to the Dominion's benefit, and, for that, Thot Gor was given a lot of favor. He negotiated a secret protocol in the treaty for territorial concessions from Cardassia as well as access to all Cardassian databases, each over Damar's protest. He oversaw the Breen forces, and also was given authority on all military recommendations, including from Damar. This incensed Damar greatly.
Gor went to work right away, recommending taking advantage of several weak points on the Romulan border, including the Unroth system. He also ordered a daring Breen attack on Earth. He later oversaw the Second Battle of Chin'toka, which was a remarkable victory for the Dominion. (DS9: "Strange Bedfellows", "The Changing Face of Evil")
Through these successes, Gor had an even closer relationship with Weyoun and subtly insulted Damar. Damar warned Gor that the Breen would be blamed, just as Cardassia currently was, for any failures. Gor defiantly did not expect any failures to happen. He also intrigued Weyoun – for example, by saying that Breen was not particularly cold but then not revealing to him the real reason for refrigeration suits which the Breen soldiers wore at all times.
Gor watched, along with Weyoun and the Female Changeling, as Damar sent out a transmission calling for the beginning of the Cardassian Liberation Front. Gor was subsequently tasked with finding Damar, no matter the cost. (DS9: "The Changing Face of Evil")
Thot Gor was played by Todd Slayton.
In the first draft script of "The Changing Face of Evil", Gor communicated that he didn't care if Weyoun 8 was the last of the Weyoun clones, though this doesn't happen in the final version of the episode.
Gor was present in the first draft script of "Tacking Into the Wind", though Pran had replaced him in that part by the time the final draft of the teleplay was written. However, Gor's name remained in the script's cast list. 
It is unknown exactly what happened to Gor and why Pran succeeded him. According to Todd Slayton, Gor's abrupt exit was because he appeared "too skinny to be a supreme leader."  According to StarTrek.com, Pran was simply "an associate of Thot Gor".