Planet: name unspecified. The Breen are a reclusive, powerful, and warlike humanoid race, native to the planet Breen in the Alpha Quadrant. Shrouded in mystery, the Breen are one of the most underestimated races inhabiting the Alpha Quadrant.

Historically, the Klingons were among the first to discover the consequences of underestimating the Breen. During the Klingon Second Empire, Chancellor Mow'ga ordered an entire fleet of Klingon warships to invade and conquer the Breen home world. The fleet never returned and was never heard from again.

Even in the 24th century, much is still unknown about the Breen and their otherwise politically nonaligned government, known as the Breen Confederacy. The Federation, however, have limited knowledge of the Breen and are aware of Breen outposts located near a black cluster in 2368. In 2370, the Breen participated in a palio held at Deep Space 3, during which the Ferengi attempted to bribe the Breen pilot into throwing the race.

In 2373, the Breen settlements on Portas V near the Demilitarized Zone dealt with the Maquis, supplying them with cold-storage units. Breen privateers during the 24th century would often conduct indiscriminate raids against other Alpha Quadrant species. This includes the Breen attack and capture of the Cardassian transport Ravinok in 2366. The survivors of that attack were used for slave labor in the Breen operated dilithium mines on Dozaria.

Alliance with the Dominion
In 2375, the Breen moved from a policy of low-level hostilities toward other major powers to one of open warfare when they allied themselves to the Dominion. They were then allowed access to the Dominion military database. According to the terms of the alliance, the Breen Confederacy received several planets in the Cardassian Union as compensation for joining the war.

The Breen may have been influenced to join the Dominion by a Changeling impersonator in the Confederacy's government, as an unidentified Breen was seen in Internment Camp 371, where several people replaced by Changelings were placed.

Shortly after joining with the Dominion, the Breen attacked Starfleet Headquarters on Earth in the raid on San Francisco. A short time later they assisted the Dominion forces in breaking the lines at Chin'toka. Under orders from the Female Changeling they allowed the escape pods to carry the Federation survivors to safety. This major battle, known as the Second Battle of Chin'toka, was won by the Dominion thanks to a unique Breen weapon, a form of energy dampening weapon system which could completely drain all the main power systems of a starship. Both of these defeats dealt a huge blow to the Allies' morale. The only ship immune to the Breen weapon was a Klingon Bird-of-Prey, which serendipitously survived thanks to an adjustment the main engineer had made to the ship's tritium intermix in the warp core.

Although the Klingon fleet was able to make the needed adjustments against the weapon, the Federation and the Romulans were still unable to defend against the Breen. When the Federation finally did create a defense against the energy-dampening weapon, they would force the Dominion fleet to retreat. Breen Thot Pran expressed an extreme distaste of surrender, and would require the reassurance of the female changeling that they were not surrendering, but instead regrouping and attempting to redouble their shipbuilding and replenishment efforts.

With the necessary counter measures to the Breen's energy dampening weapon obtained, the Federation Alliance was able to go on the offensive once again, choosing to invade Cardassia Prime itself. In hopes of boosting the Breen's will to fight, the Female Changeling offered them control of Earth and Romulus if they succeeded in winning the battle. During the Battle of Cardassia, the Breen were still able to inflict major casualties on the allies, even without the use of their energy dampening weapon. Up to a third of the entire allies' fleet was destroyed during the battle, including the Romulan flag ship. The Breen continued to fight with the Dominion until the end, demonstrating a willingness to die for the cause that matched that of the Jem'Hadar. However, when the Cardassian forces switched side’s mid-battle, the Dominion and Breen were forced to withdraw to Cardassia Prime. After Odo convinced the Female Changeling to surrender, the Dominion War ended. As a member of the Dominion, the Breen leaders were present during the Treaty of Bajor.


Breen physiology is among the most exotic for humanoid life forms, which may be due, in part, to their home world’s climate. The Breen have no blood or other liquid circulatory system. The Breen brain is structured into four lobes; this protects them from the probing of some empathic species, such as the Betazoids, who are unable to detect the thoughts or emotions of the Breen.

Breen appear physically more resilient than most humanoids. When Worf struck a Breen, the Breen proceeded to incapacitate Worf with a neural truncheon, seemingly oblivious to the assault. The Breen constantly wear refrigeration suits in order to maintain a cold temperature like that on their home world. According to Worf, no outsider had ever seen what a Breen looked like under their refrigeration suits and lived. Even after joining the Dominion, their appearance was unknown to their new allies. Weyoun couldn't help but wonder what they looked like.

The Breen commonly produce offspring at a very early age, at about the equivalence in physical growth of Human third grade children. The Breen entertain their offspring with nursery rhymes. Breen nursery rhymes can be made up of a heterophonic, five-line verse with an alternating tetrameter and pentameter structure. These are nonsensical phrases strung together because they rhyme (at least to the Breen). Some Breen music, which can accompany these nursery rhymes, is written on a Lyxian scale.

Treatment of Prisoners:

The Breen are known to use slave labor; and at least some of these slaves are captured in raids on other species. When the Breen were using Bajorans slaves to mine dilithium ore, there were always at least eight guards within the mines. The Breen are very prudent when dealing with prisoners. When capturing prisoners, the Breen typically stun them from long range with their disruptors, rather than approaching them and risking close combat. When Worf and Ezri Dax were discovered by the Breen on Goralis while sleeping, the Breen used this technique to subdue them. The Breen feed their prisoners a diet of algae paste, as well as hang them upside down to ensure they cannot escape. On board starships, the Breen typically send in three guards at a time when they wish to remove a single prisoner from a cell that is being shared with other prisoners. Worf's various attempts at escape always failed, including his attempt to persuade the Breen guards that Ezri was sick, as well as his attempt to short-circuit the door. When Worf attempted to attack the Breen guards, they used a type of neural truncheon to paralyze him. Even after he fell to the ground, partially paralyzed, two Breen guards continued to use the truncheons on him to ensure he would not get back up, before two guards removed Ezri from the cell. In another incident, Worf simply showed signs of anger towards Weyoun and was again shocked by the neural truncheon.

Science and Technology

Given that most known humanoid species live on class M planets with an average temperature far above the supposed temperature of Breen, the Breen are largely thought to have had to develop refrigeration suits in order to co-exist with others. However, if the Breen home world is temperate as suggested by Weyoun, then their reason for wearing environmental suits, if they were environmental suits at all, was much more mysterious. The Breen are known for their knowledge of sophisticated cold-storage units, summed up in Captain Sisko's statement, "If anyone knows how to keep things cold, it's the Breen."

During the 2360s, the Breen were known for their development of organic technology, which they employed in the construction of their spacecraft

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