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
The Breen warship was designed by John Eaves and rendered as a CGI model. Eaves commented: "Designing the Breen ship has an interesting origin. The Breen are a race that have no established architecture, therefore it opened the door to me to be extremely creative. My initial pass had the ship loosely around the letter 'T'. The story behind the 'T' is that it is the first letter of my fiance's name, Tara. I submitted the drawings and the producers liked the shape and requested more detailed drawings. When these were presented, the producers requested the drawings go a different direction than the original 'T' shape. Therefore, I started designing 'T' ships with a more stylish letter formation - lower case 't's', 't's' hidden among other shapes, etc. Each design sparked enthusiasm with the producers, yet they still wanted to see more fantastic ideas. So, after several more passes, they chose a drawing I didn't think they would choose. It broke all the traditional rules that Star Trek ships are required to meet. The 'T' ship, as I call it, is an open-faced, multiple plane swept wing conglomeration of weapons and engines and a big fat 'T' right in the centre. If you know where to look, all of the letters of Tara's name can be found in the detailed panelling of the ship's exterior. This has been my favorite of all designs for DS9 because of the inspiration which went into its design". ("Far Beyond the Drawing Board", Star Trek Monthly issue 54)
In the novelization of "What You Leave Behind", Worf mentions that the Breen warships were equipped with "stochastic field emitter at Memory Beta, the wiki for licensed Star Trek workss" which improved the resilience of their shielding.
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. A playable version of this vessel, named the "Breen Chel Grett Warship", was released as part of the 2012 winter event and could be redeemed for 1,000 "Autographed 8x10 Glossy Picture of Q".