The Mirror Universe is one of Star Trek's most intriguing concepts with its own rich and fascinating history. Introduced in Star Trek: The Original Series season 2, the Mirror Universe has been used sparingly so that each appearance is an event. The alternate reality where nearly every beloved Star Trek character is the opposite of who they are in Star Trek's Prime Universe spans five TV series: TOS, Star Trek: Deep Space Nine, Star Trek: Enterprise, Star Trek: Discovery, and Star Trek: Prodigy. The Mirror Universe is also very different from the Kelvin timeline of J.J. Abrams' Star Trek movies, which diverges from the Prime timeline at a fixed point in the 23rd century.
The history of Star Trek's Mirror Universe unfolds confusingly. After its lone 23rd-century Star Trek: TOS episode, "Mirror, Mirror," Star Trek: Deep Space Nine picked up the Mirror Universe's story in the 24th century. Star Trek: Enterprise then jumped backward 200 years with a 22nd-century prequel tale. Star Trek: Discovery season 1 returned to the Mirror Universe in the 23rd century, a decade before TOS, before it jumped to the 32nd century and filled in some details of what became of the Mirror Universe in the last 800 years. Finally, Star Trek: Prodigy season 2 updated the state of the Mirror Universe after DS9. For clarity's sake, here is what happened in the Mirror Universe chronologically from before First Contact with the Vulcans to what is known about the alternate reality in the 32nd century.
How Star Trek's Mirror Universe Is Different From The Prime Universe
It's not quite a mirror.
Star Trek's Mirror Universe runs parallel to the Prime Universe's because both realities co-exist in the same space but in different dimensional planes. The variances between people from the Prime and Mirror Universes are primarily cultural, with Mirror counterparts hewing towards malevolence and bigotry. However, there is also at least one distinct physical difference between the two universes: In Star Trek: Discovery season 1, Michael Burnham (Sonequa Martin-Green) noticed that "the cosmos has lost its brilliance"in the alternate reality. Burnham didn't just mean metaphorically; the Mirror version of Captain Gabriel Lorca (Jason Isaacs) needed eye drops due to his photosensitivity to the light in the Prime Universe.
The Federation and the Terran Empire know of each other's existence.
In Star Trek's Mirror Universe, instead of the United Federation of Planets, humanity formed the Terran Empire and successfully conquered the Alpha Quadrant in the 22nd and 23rd centuries. The Federation and the Terran Empire know of each other's existence but suppress this information to prevent further crossovers. The Mirror Universe's Terran Empire was ruled by an Emperor. While Federation starships are designated USS, in the Mirror Universe, Terran vessels carry the designation ISS (Imperial Starship). However, the Terran Empire collapsed by the 24th century and was overrun by their enemies, the Klingons and the Cardassians, which formed an alliance along with other worlds like Bajor.
How The Mirror Universe's Terran Empire Rose To Power
The Mirror Universe's First Contact was very different
On the Mirror Universe's Earth, history unfolded in a mostly identical fashion as in Star Trek's Prime Universe, except the human race embraced war and fascism as a means to solve problems. Mirror Earth's history involved nations going to war, with the strong overcoming the weak, until the pivotal date of April 5, 2063. This was the day of First Contact with the Vulcans, who landed in Boseman, Montana after Zephram Cochrane (James Cromwell) became the first human to achieve warp flight.
Cochrane immediately executed the Vulcan visitor with a shotgun.
However, instead of a peaceful meeting as had occurred in the Prime Universe, which fans saw in Star Trek: First Contact, in the Mirror Universe, Cochrane immediately executed the Vulcan visitor with a shotgun, believing this was the first step of an alien invasion of Earth. (Cochrane's shotgun later came to be owned by the Mirror Jonathan Archer.) Cochrane's people then raided the starship and executed the other Vulcans aboard. With Vulcan technology, the human race took to the stars, establishing the Terran Empire within the next century. The Terrans conquered and enslaved many of the other races in the Alpha Quadrant, and the xenophobic human-led empire lasted for almost 300 years.
Star Trek's 22nd Century Mirror Universe
As seen in Star Trek: Enterprise season 4
Star Trek: Enterprise's "In A Mirror, Darkly" revealed that in 2155, Commander Jonathan Archer (Scott Bakula) mutinied against his Captain, Maximillian Forrest (Vaughn Armstrong), and took command of the Terran Empire's flagship, the ISS Enterprise. Archer's scheme involved taking the Enterprise into Tholian space to retrieve the USS Defiant (NCC-1764), a Constitution Class starship that time-traveled from the 23rd-century Prime Universe to the 22nd-century Mirror Universe in the Star Trek: The Original Series episode "The Tholian Web."
The USS Defiant (NCC-1764) is unrelated to the USS Defiant in Star Trek: Deep Space Nine.
With the Terran Empire in danger of losing a war against its many enemies, Archer's ambition was to use the far more powerful USS Defiant from the alternate reality to stage a coup where he would become the new Terran Emperor. The Enterprise (and Captain Forrest) were destroyed by the Tholians, but Archer succeeded in commandeering the Defiant. However, Archer was betrayed and killed by his mistress, Hoshi Sato (Linda Park). Sato then took command of the Defiant and completed Archer's coup, declaring herself Empress.
Star Trek's 23rd Century Mirror Universe
As seen in Star Trek: Discovery seasons 1 and 3
100 years after Star Trek: Enterprise, Star Trek: Discovery season 1's Captain Gabriel Lorca (Jason Isaacs) revealed himself to be a Terran from the Mirror Universe. Lorca used the USS Discovery's spore displacement hub drive to return to the alternate reality. However, he wanted Michael Burnham to help him stage a coup to dethrone the Terran Emperor Philippa Georgiou (Michelle Yeoh). Burnham and the crew of the USS Discovery posed as their Mirror Universe counterparts in order to survive being trapped in the parallel dimension.
By 2257, the Terran Empire was the dominant power in the Alpha Quadrant and, under Georgiou's rule, the humans conquered the Klingons, although a band of alien races formed a rebel alliance against the Terrans. Georgiou also knew about the Prime Universe and the Federation because she had access to the USS Defiant's data files. But Georgiou's gravest threat was Lorca, who nearly succeeded in his coup. At the end of Star Trek: Discovery's four-part saga in the Mirror Universe, Lorca was killed and Georgiou's reign was ended, but Michael Burnham brought the evil doppelgänger of her late Captain Georgiou back with her to the Prime Universe.
Starfleet identified a chimeric strain on the subatomic level in the Terran stem cell, which explains the Terran predisposition towards malevolence.
After the USS Discovery time traveled to the 32nd century Georgiou was personally debriefed by Doctor Kovich (David Cronenberg). During their meeting, Kovich updated Georgiou, who knew nothing of the events seen in Star Trek Deep Space Nine, on the state of the Mirror Universe. Kovich revealed that the distance between the Mirror Universe and the Prime Universe had been increasing for centuries, which has prevented crossovers. In fact, no one had jumped from either reality for 500 years. Kovich also informed Georgiou that Starfleet identified a chimeric strain on the subatomic level in the Terran stem cell, which explains the Terran predisposition towards malevolence.
With Emperor Georgiou dying from crossing both time and realities, the Guardian of Forever (Paul Guilfoyle) tested her worthiness. Georgiou returned to the Mirror Universe in the 23rd century, where she realized she had changed from her time with the compassionate Michael Burnham in Star Trek's Prime Universe. The Guardian of Forever was satisfied with Georgiou's newfound perspective and sent the Emperor back to a time when the Prime and Mirror Universes had not yet permanently diverged. Georgiou's story will continue in Star Trek: Section 31.
Star Trek's Mirror Universe In The 23rd Century
As seen in Star Trek: The Original Series Season 2 and Star Trek: Discovery Season 5
Star Trek: The Original Series season 2's "Mirror, Mirror" was the first appearance of the Mirror Universe that started it all. Chronologically set a decade after Star Trek: Discovery season 1, a transporter accident switched the Prime Universe's Captain James T. Kirk (William Shatner) and three of his officers with their Mirror Universe counterparts. While the USS Enterprise's Spock (Leonard Nimoy) quickly imprisoned the evil duplicates of his crewmates, aboard the ISS Enterprise, Kirk had to navigate the dangerous political waters of the Terran Empire, where assassinating your superior officers and rivals is the key to advancement and power.
Kirk challenged Mirror Spock to do what he could to change the destiny of the Terran Empire.
As Kirk grasped the profound differences between the two universes, he realized that the goateed Mirror Spock harbored grave doubts about the longevity of a fascist regime like the Terran Empire, which the Vulcan calculated was doomed to totally collapse within 240 years. Before switching back to his proper universe, Kirk challenged Mirror Spock to do what he could to change the destiny of the Terran Empire.
In the greater context of the overall Mirror Universe's history, Star Trek: Discovery season 2 revealed that the Prime Universe's Spock already knew what the Mirror Universe was thanks to his adopted sister Michael Burnham's experiences and from meeting Emperor Georgiou. As part of his lifelong pact never to reveal the truth about Burnham or the USS Discovery, Spock's swift and decisive actions when he meets Mirror Kirk become recontextualized since the Vulcan knew precisely where this evil version of his Captain came from.
Star Trek: Discovery season 5, episode 5, "Mirrors," picks up Mirror Spock's story when Captain Michael Burnham and Cleveland Booker (David Ajala) find the derelict ISS Enterprise in interdimensional space and pilot it into the 32nd century. Book and Burnham learned that Mirror Spock's attempts to reform the Terran Empire failed, and the Vulcan was assassinated. A group of refugees inspired by Mirror Saru (Doug Jones) hijacked the ISS Enterprise in an attempt to flee into the Prime Universe. Although the Enterprise was left abandoned, the Mirror refugees did make it into the Prime reality and started new lives.
Star Trek's Mirror Universe In The 24th Century
As seen in Star Trek: Deep Space Nine and Star Trek: Prodigy Season 2
Star Trek: Deep Space Nine continued the story of the Mirror Universe in the 24th century for five episodes throughout its seven seasons. DS9's first Mirror Universe episode, "Crossover," revealed that the Terran Empire was conquered by the Klingon and Cardassian Alliance. Following Mirror Spock's takeover and failed bid for peace, the vulnerable Terrans were overrun by their alien enemies. Terrans became slaves in the 24th century, fighting a rebellion against the Klingons and Cardassians. Ironically, whereas Spock's legacy was the reunification of the Vulcans and Romulans in Star Trek's Prime Universe, Mirror Spock's attempt at nobility caused the demise of the mighty Terran Empire.
"Smiley," the Mirror Miles O'Brien, emerged as a central character of DS9 's Mirror Universe story.
DS9's Mirror Universe saga was intensive, with characters crossing over into both universes, and the action revolved around the Deep Space Nine space station, which was still known as Terok Nor in the Mirror Universe. In "Through the Looking Glass," Commander Benjamin Sisko (Avery Brooks) had to briefly replace his dead counterpart, who was the Terran resistance's leader in the Mirror Universe. Meanwhile, "Smiley," the Mirror Miles O'Brien, emerged as a central character of DS9's Mirror Universe story; Smiley not only recruited the Prime Sisko, but he also stole the plans for the USS Defiant from Deep Space Nine so that the Terran rebels could have a warship of their own.
Word of the Mirror Universe eventually reached the Ferengi Alliance and Grand Nagus Zek (Wallace Shawn) jumped to the Mirror Universe in order to open up business opportunities. The Terrans' main enemy was the Klingon and Cardassian Alliance's Regent, who was revealed be Worf (Michael Dorn). The Regent was eventually overthrown by the rebels in DS9's final Mirror Universe installment, "The Emperor's New Cloak." DS9's Mirror Universe story left off with the Terran rebels still fighting to bring down the Klingon and Cardassian Alliance.
Star Trek: Prodigy season 2, episode 14, "Cracked Mirror," is now the furthest known point of the Mirror Universe's saga. "Cracked Mirror" revealed that after Star Trek: Deep Space Nine, the Terran Empire rose again in the late 24th century. Adopting their old ways and forming a new Terran Armada, humans once again began conquering the galaxy. Briefly crossing over into the Mirror Universe, Captain Chakotay (Robert Beltran) and the young crew of the USS Protostar found themselves aboard the ISS Voyager-A and become prisoners of the Mirror versions of Admiral Kathryn Janeway (Kate Mulgrew) and Captain Chakotay. After Mirror Janeway teamed up with the Protostar's heroes to repel the timeline-consuming threat of the Loom, what's next for Star Trek's Mirror Universe remains to be seen.
