In 2366, two Breen warships attacked the Cardassian transport Ravinok forcing it to crash-land on the planet Dozaria. Its survivors were forced to work in a nearby Breen dilithium mine. (DS9: "Indiscretion")
In late 2375, the Breen became allies of the Dominion, where they committed a large fleet of warships to join the war effort. Worf and Ezri Dax were brought aboard a warship after being captured by the Breen on a planet in the Goralis system. (DS9: "Penumbra", "'Til Death Do Us Part")
The Federation first encountered the ships in combat during the Second Battle of Chin'toka. The Cardassian and Dominion ships held back while the Breen engaged the Federation, Klingon and Romulan forces. The ships had been equipped with energy dissipators that disabled the Allied ships' engines, weapons, and shields. The weapon was instrumental in defeating the Allied fleet and forcing the Federation Alliance from the Chin'toka system, losing the only enemy territory that they held in Cardassian space. (DS9: "The Changing Face of Evil") Fortunately, the Klingon Bird-of-Prey IKS Ki'tang was not affected, leading to a defense being discovered. (DS9: "When It Rains...")
Even without the energy dampening weapon, the Breen warships proved to be formidable. One such ship destroyed Legate Damar's ship in orbit of Cardassia Prime. Several warships participated in the Battle of Cardassia. During this engagement, a Breen warship was able to outmaneuver the USS Defiant, displaying exemplary maneuverability. Besides the energy dissipator, Breen warships mainly attack with torpedo weapons fired from at least three forward launchers at the pikes of the ship. Several Breen warships were destroyed by the Cardassian fleet when the Cardassians joined the Allies. Breen warships were also deployed in orbit of Cardassia Prime after the Dominion's retreat. (DS9: "The Changing Face of Evil", "The Dogs of War", "What You Leave Behind")
Ships of the class
Eaves discusses the creation of the ship in the special features of the DS9 Season 7 DVD. In the interview, he reveals that the ship was based on the shape of the letter "T" after the initial of his wife's first name. The ship was a departure from the usual angular ships previously seen and is one of Star Trek's more unusual ships.
In the unpublished Last Unicorn Star Trek Roleplaying Game sourcebook DS9 The Dominion War Sourcebook - The Fires of Armageddon, the Breen Warship is referred to as the Gor Taan class.
The Star Trek Customizable Card Game gives Gor's warship's name as Tykk.
Breen Warships appear in Star Trek Online as a part of the game's "Season Two" update, along with several other Breen vessels unique to the game. The warship itself is referred to as the Chel Grett class, a name which also fares from the Fires of Armageddon sourcebook. The other Breen ships featured in the update also borrow names from the sourcebook. The ships in Star Trek Online appear with polaron weaponry as well as transphasic torpedos.