Mirror universe cultures

Aenar
The Aenar were an Andorian ethnic subgroup with a history of enmity towards Andorians. In, they aided the Terran Empire's conquest of Andoria, hoping to gain advantage over the Andorians, to mixed results. They later aided the Terran rebellion, but again suffered at the hands of the second empire, which decimated most of the Aenar between late 2385 and early 2386, in response to the actions of Shran ch'Rothress. By 2386 the Aenar had been exiled from Andoria and driven to the brink of extinction. 

Andorians
An Andorian male crewmember, possibly a conscript, worked aboard the ISS Avenger serving at the helm. He was killed while aiding fellow non-Terrans under Soval in an attempt to destroy the USS Defiant. (ENT: "In a Mirror, Darkly, Part II")
 * Presumably, the Andorians were conquered by the Terran Empire.

In, after being freed from Terran Empire rule, Andoria became part of the Klingon-Cardassian Alliance. By the 2370s however, the Andorians resented the Alliance (Klingons in particular). Many supported and fought with the Terran rebellion against the Alliance, then joined the Imperial Union of Planets afterwards. 

Bajorans
The Bajorans were a race conquered by the Terran Empire. Bajor became a sovereign member of the Klingon-Cardassian Alliance following liberation by Alliance forces; some Bajorans, however, joined the Terran rebellion (DS9: "Crossover", "The Emperor's New Cloak" et al.); in A Debt of Honor Bajor's vedeks had sheltered many of the rebels on Terok Nor, often at great risk to their own lives. In, Bajor betrayed the Alliance and joined the Imperial Union of Planets.

Bartokians
The Bartokians were subjugated by the Imperial Union of Planets in 2385. 

Betazoids
Betazoids once tried to use their abilities for personal gain in the Terran Empire, but because the Empire distrusted telepaths, met with stiff resistance. They joined the Alliance until the late 2370s. Foreseeing the Alliance's demise, they switched sides and joined the Imperial Union of Planets. Betazoid dissidents tried to engineer Betazed's secession from the IUP in 2385, but were unsuccessful. 

Bolians
The Bolians were heavily subjugated by the Terran Empire. In the late 24th century they joined the Imperial Union of Planets. 

Borg
The Borg were one of three founding members of the Alliance of Independent Governments. They were slightly less sophisticated and had a significantly smaller population than those in the primary universe; yet still possesed transwarp drive and minor cybernetic enhancments. 

In, the Imperial Union of Planets sought for years to fashion mirror-equivalents of the Borg for servitude and soldiery, without success. In 2385, Starfleet officers on the ISS Arcadia succeeded in creating Borg drones by obtaining Borg nanoprobe schematics from the Federation universe. These Borg soon ran amok and became a threat. Apparently their threat was neutralized by 2386, though in what manner remains unclear.

Breen
Very little is known about the Breen of the mirror universe. Intendant Kira once told Benjamin Sisko that Breen icicles were warmer than Jennifer Sisko. (DS9: "Shattered Mirror")

Caitians
Caitians served aboard Imperial starships of the late 24th century. 
 * It was never clear whether they formally belonged to the Imperial Union of Planets.

Cardassians
The Cardassians were a founding race of the Klingon-Cardassian Alliance. (DS9: "Crossover", et al.)

Changelings
In the mirror universe the Bajoran wormhole remained undiscovered as late as 2375. Thus Changelings and other species native to the Gamma Quadrant remained unknown to peoples of the Alpha Quadrant, with the exception of Odo, who was killed on Terok Nor during a workers' revolt in 2370. (DS9: "Crossover")
 * ''Probably, Odo was, like his counterpart, one of "the hundred" and was found in the Denorios Belt.

Cygnians
The Cygnians were once ruled by the Terran Empire, then later became a member race of the Imperial Union of Planets. Several served in the Imperial Starfleet. 
 * This race was identified as the lavender-skinned species seen in "Journey To Babel" (TOS), although canon does not confirm this.

Denobulans
Denobulans were a slave race of the Terran Empire. Phlox served aboard the ISS Enterprise as ship's doctor. Denobulans were not part of the rebellion against the Empire, as it was not in their nature. (ENT: "In a Mirror, Darkly, Part II")

Ferengi
The Ferengi were, for the most part, seen as far more compassionate and less greedy than their counterparts in the "primary" universe, often paying for this compassion with their lives. The Terran Empire ravaged their homeworld in the 23rd century, while in A Debt of Honor Ferengi dilithium shipments helped the Alliance defeat the Empire. The Alliance oppressed them during the 2370s and some Ferengi were members of the rebellion. (DS9: "Crossover", et al.)

First Federation
In 2387 the First Federation was a tyrannical power located on the edge of Terran space. They employed slave labor. Many soldiers from the Klingon-Cardassian Alliance were imprisoned here when the New Terran Empire took shape. (Star Trek: Pioneer: "Dark Reflection", "A Mirror, Shattered")

Gorn
A Gorn named Slar was a slave master working for the Tholian Assembly. He was in charge of the workers assigned aboard the USS Defiant until the crew of the Enterprise took it over. Slar was seen as untrustworthy of humans and vicious when it came to dealing with them. He was ultimately killed by Jonathan Archer. (ENT: "In a Mirror, Darkly, Part II")

Some Gorn worked in various capacities both in and out of Starfleet in the late 24th century. See: Sselraan, Ssslon. 

Halkans
Like their counterparts, the Halkans are a peaceful race, avoiding violence at all costs ("TOS: "Mirror, Mirror"). In A Debt of Honor their pacifism became a role model for Spock's reform efforts, but it led to Spock's being overthrown by the Imperial Starfleet.
 * ''This appears to be one of the rare examples of races being virtually identical in both universes.

Hirogen
A founding race of the Alliance of Independent Governments.

Iroids
One of the Iroids, Imirissen, served on board the ISS Imperia in 2386. 

Klingons
The Klingons were a founding race of the Klingon-Cardassian Alliance. (DS9: "Crossover", et al.)

In, the Klingons were virtually wiped out by 2386, robbed of political and military power after years of siege by the Imperial Union of Planets. Klingon resistance cells continued to operate, however, often in collusion with Romulans. 

Naish
The Naish were known for their love of wealth and splendor. A Naish dilettante visited Risa in 2385. 

Orions
An Orion female crewmember, possibly a conscript, worked aboard the ISS Avenger. She was killed while aiding fellow non-Terrans under Soval in an attempt to destroy the USS Defiant. (ENT: "In a Mirror, Darkly, Part II")
 * It is not stated, but implied that the Terran Empire annexed the Orions by 2155. Another theory is that the Orion Syndicate were allies. Either way, the Empire presumably discovered some sort of protection against the Orion females' pheromones, or they lack the pheromones in the mirror universe.

In the late 24th century, Orions commonly served in Starfleet, while others led lives as pirates. 
 * In, the Empire indeed suppressed Orion females' pheromones, via prescribed medical injections. This was a requirement of all Orion females in Starfleet service.

Remans
The Remans served as soldiers in the Romulan Technocracy, to which they supplied Reman warbirds. Their status following the fall of Romulus to the Empire remains unrevealed. 
 * In, Remans were classified as genetically engineered offshoots of the Romulans.

Richtor's species
A member of this unnamed humanoid species, known for black spiral-shaped pupils, served aboard the ISS Arcadia in 2385. 

Romulans
The Romulans appeared to be uninvolved in the conflict between the Terran rebellion and the Klingon-Cardassian Alliance. The primary Benjamin Sisko, portraying his mirror counterpart, indicated to Jennifer Sisko that he would visit the Romulans in an attempt to gain their support. This was, in actuality, a ruse to explain his return to Deep Space 9. (DS9: "Through the Looking Glass")

In, the Romulan Technocracy became the governing regime of the Romulans as the result of a disastrous clash with the Terran Empire. By 2386 Romulus had joined the Imperial Union of Planets. 

In continuity, there never existed a Romulan Empire in the mirror universe. Instead the Romulans formed the Romulan Star Republic, a much less xenophobic and territorial power. In 2390 the New Terran Empire planned to conquer the republic. (: "Infinite Empires")

Suliban
The ISS Enterprise had contact with the Suliban by January 2155, acquiring a cloaking device from this species. (ENT: "In a Mirror, Darkly")
 * The circumstances of the encounter went unrevealed.

Tellarites
The Tellarites were apparently conquered by the Terran Empire sometime before 2155 and some had joined the rebellion against the Empire. Malcolm Reed and Phlox tortured a Tellarite crewman named Terev in the agony booth as a demonstration of the device for ISS Enterprise captain Maximilian Forrest and Commander Jonathan Archer. (ENT: "In a Mirror, Darkly")

In, the Tellarites later joined the Imperial Union of Planets.

Terrans
In the mirror universe, humans were filled with fear and suspicion when a Vulcan scout ship landed on Earth to initiate first contact. The humans slaughtered the Vulcan crew and used the technology within to create an interstellar empire. This Terran Empire lasted almost three centuries until it was overshadowed by the equally vicious aspirations of Klingons, Cardassians, and Bajorans. Although many races in the mirror universe harbored hopes of forming a peaceful alliance to protect civilization, Terrans were rarely found among these rebels due to the wealth and safety afforded by their violent expansionist policies.

Tholians
There appeared to be no open hostilities between the Terran Empire and the Tholians in 2155, though the Tholians were known to annex systems close to their space. A single Tholian starship was no match for an NX class vessel like the ISS Enterprise (NX-01) though several of these vessels were capable of destroying such a vessel, particularly when employing a Tholian web. (ENT: "In a Mirror, Darkly")
 * It's unclear what the long-term consequences were for a Terran Empire ship invading Tholian space, stealing the Defiant, and destroying several of their ships.

Trill
It is unclear which side (if any) the Trill government took in the conflict between the Alliance and the rebellion. A number of individual Trills, such as Jadzia, joined the rebellion, while others such as Ezri Tigan sought to remain non-aligned. (DS9: "Through the Looking Glass", et al.)

In, Trill symbionts were not revered, but seen as parasites, under the belief that "joining" was a form of mind control. A war early in their history eradicated most of the symbionts. By 2385 the planet Trill had joined the Imperial Union of Planets. 

Voth
A founding race of the Alliance of Independent Governments.

Vulcans
In 2063, when the Vulcans made first contact with Earth, Zefram Cochrane shot the first Vulcan to set foot on Terran soil. The Terrans stormed the T'Plana-Hath and studied Vulcan technology. Eventually, the Terran Empire was able to conquer the Vulcans. (ENT: "In a Mirror, Darkly")

By the 2150s, Vulcans were considered slaves to Terrans and not treated as equals. A number of Vulcans and Vulcan ships rebelled against the Terran Empire. By 2267, their attempts seemed to have been unsuccessful, although it appeared that Vulcans such as Spock were treated with more respect and feared by some Terrans. (ENT: "In a Mirror, Darkly, Part II", TOS: "Mirror, Mirror")

In the 2370s, Vulcans served as slaves to the Klingon-Cardassian Alliance. Several were seen fanning the Intendant on Terok Nor. (DS9: "Crossover") Some Vulcans, such as Tuvok, joined the Terran rebellion. (DS9: "Through the Looking Glass")
 * Jonathan Archer mentioned humans turning the tables on the Vulcans' invasion force. This might have been an assumption based on Archer's paranoia (or government propaganda).

In, Spock's reforms, which became known as "Spock's folly", led to the destruction of the Terran Empire and the enslavement of humans, earning Vulcans a negative social stigma. Although many supported and fought with the Terran rebellion, they were widely regarded with loathing and suspicion in the Imperial Union of Planets, which they joined purely to avoid destruction at the "new Empire"'s hands. In this continuity, the Alliance ravaged Vulcan much as it had Earth, albeit not quite as badly. 

Xindi
The Xindi fought in a conflict with the Terran Empire sometime prior to 2155. (ENT: "In a Mirror, Darkly", Parts I & II)
 * Seen in the opening credits for those episodes.