The Mirror Universe was first introduced in the “Star Trek: The Original Series” episode “Mirror Mirror.” In that episode, a transporter accident sent Captain Kirk, Dr. McCoy, Lieutenant Uhura, and Chief Engineer Mr. Scott to an alternate universe. Upon their arrival, the Enterprise crew members discovered that they were on an alternate version of the Enterprise filled with alternate versions of the people with whom they served. This led them to dub the alternate universe “the Mirror Universe.”
Kirk, McCoy Uhura, and Scotty also discovered that the political and social climate was much different in this alternate universe. The tyrannical Terran Empire ruled the quadrant with ruthlessness and violence.
Since the Mirror Universe was first introduced, it has played a major role in three other “Star Trek” shows. Five episodes of “Star Trek: Deep Space Nine” were either set in the Mirror Universe or included characters from the Mirror Universe. Two episodes of “Star Trek: Enterprise” were set in the Mirror Universe. Most recently, “Star Trek: Discovery” did a multi-episode storyline set in the Mirror Universe, and introduced the first Mirror Universe counterpart to stay in the Prime Universe.
Coming up with a cohesive timeline of the Mirror Universe is tough for many fans because each show depicted a different time period in that universe. TOS showed the Mirror Universe in the 2200s, DS9 depicted the Mirror Universe in the 2300s, “Enterprise” portrayed the Mirror Universe in the mid-2000s and 2100s, and “Discovery” took fans back to the Mirror Universe in the 2200s before Kirk and his crewmates discovered it.
So, it can be hard to keep track of what happened and when in the Mirror Universe, especially for fans watching the shows in the order they aired. So, we’ve created this guide to the biggest events in the Mirror Universe history and which episodes depict them.
The Mirror Universe in the 2000s and 2100s
Prior to First Contact:
The exact date that the Terran Empire rose to power in the Mirror Universe hasn’t been revealed in the “Star Trek” canon. In “Enterprise” two-parter “In a Mirror, Darkly,” Commander Jonathan Archer said that the Terran Empire had existed for centuries as of the 2100s. In the “Discovery” episode “Vaulting Ambition,” Emperor Phillipa Georgiou hinted that the Terran Empire had been around for millennia.
2063: First Contact
Just as he had in the Prime Universe, Mirror Universe Zefram Cochrane piloted the first successful warp flight in 2063. However, the greeting he gave the Vulcans was much different than his Prime counterpart’s. The episode “In a Mirror, Darkly” showed Mirror Cochrane shooting the Vulcan delegation and ordering his crew to loot their ship.
2063-2155: Terran Empire Rises to Power
“In a Mirror, Darkly” and “In a Mirror, Darkly Part II” revealed that the Terran Empire took control of the Alpha Quadrant sometime in the late 2000s or early 2100s. The conflict that ended with the Terran Empire’s supremacy began when the Lunar Colonies were attacked. The Terran Empire used this as an excuse to amp up aggressions against the other Alpha Quadrant species, and it conquered the Vulcans, Andorians, Tellarites, Denobulans, and the Orions.
2155: Mutiny on the ISS Enterprise & the USS Defiant
In the same two-parter, Commander Jonathan Archer led a mutiny against his Captain, Maximillian Forrest. Archer took over the ISS Enterprise so its crew could investigate the spatial interphase that moved the USS Defiant through time and space into the Mirror Universe from the Prime Universe.
When Forrest regained control of the ship, Archer tried to use the Defiant to defeat the Enterprise. Unfortunately, he was then the subject of another mutiny led by Mirror Hoshi Sato, who declared herself Empress of the Terran Empire.
The Mirror Universe in the 2200s
The Early 2250s: The Coup Against Georgiou
In the episode “Vaulting Ambition,” Emperor Georgiou revealed that Captain Gabriel Lorca led a coup against her. She also revealed that Mirror Commander Burnham, her adoptive daughter, had joined Lorca’s attempt to overthrow the Empress.
Later in that episode, Lorca revealed that when he tried to transport back to his ship to escape, he ended up in the Prime Universe. He impersonated his Prime Universe counterpart, who was a member of Starfleet. When he heard about the experimental spore drive technology, he finagled his way into the captain’s seat of the USS Discovery, determined to make his way back to the Mirror Universe to finish what he started.
2256: Lorca and the Discovery Enter the Prime Universe
After commanding the Discovery for less than a year, Lorca finally figured out how to jump back into the Mirror Universe. In the episode “Despite Yourself,” Lorca convinced Prime Commander Burnham to impersonate her Mirror Universe counterpart and bring him to Emperor Georgiou. He told Burnham that this was the best way for them to get the information they needed to get back to the Prime Universe.
However, in the episode “Vaulting Ambition” his true intentions became clear. He wanted to get back to Georgiou’s ship so he could make contact with his supporters and lead another coup.
Commander Michael Burnham impersonated her Mirror Universe counterpart for three episodes — “Despite Yourself,” “The Wolf Inside,” and “Vaulting Ambition” — before telling Georgiou that she was actually from the Prime Universe. In the episode “What’s Past is Prologue,” Lorca tried to convince Burnham to join his coup as her Mirror counterpart had. However, she chose to assist the Emperor instead.
After they defeated Lorca, Georgiou grabbed onto Burnham just as she was being transported to the Discovery. So, she ended up on the Discovery when it transported back to the Prime Universe. Starfleet decided to cover up the fact that Georgiou was Mirror Georgiou by having her impersonate her Prime Universe counterpart.
2267: Kirk & Crew Cross Over
The very first episode about the Mirror Universe came years after the Trek canon’s first encounter with the Mirror Universe thanks to prequels like “Enterprise” and “Discovery.”
In “Mirror Mirror,” Kirk and his crew members crossed over to the Mirror Universe and impersonated their Mirror Universe counterparts. Kirk’s unwillingness to carry out the Terran Empire orders to destroy a planet led Mirror Spock to doubt whether Kirk was really his Kirk.
Eventually, Mirror Spock performed a mind-meld on Dr. McCoy and discovered that Kirk, McCoy, Uhura, and Scotty were from the Prime Universe. In a logical but uncharacteristic show of compassion, Spock let them beam back to the Prime Universe. Before they did, Kirk warned Mirror Spock that the Terran Empire would be overthrown if they didn’t find a way to govern without brutality. Spock agreed.
The Late 2200s: Spock’s Reign & Downfall
Sometime after his encounter with Prime Kirk, Mirror Spock rose to the highest seat in the Terran Empire. In the DS9 episode “Crossover,” The Intendant aka Mirror Kira Nerys informed her Prime Universe counterpart that Spock instituted sweeping reforms that weakened the Terran Empire’s control over the Alpha and Beta Quadrants.
The Klingons and the Cardassians formed an alliance to overthrow the Terran Empire, which they did relatively easily. The Bajorans joined The Alliance to protect themselves from the rampant threats in the quadrant.
The Mirror Universe in the 2300s
2370: Kira and Julian Bashir Cross Over
In that same DS9 episode, Kira and Chief Medical Officer Julian Bashir crossed over to the Mirror Universe while traveling through the wormhole. They discovered that The Alliance was in power and Terrans were used as slaves throughout the Alpha and Beta Quadrants.
Mirror Kira told Prime Kira that since Kirk had crossed over to the Mirror Universe, safeguards had been put in place to prevent crossovers, and Prime Universe counterparts were supposed to be killed on sight.
In an attempt to escape back to the Prime Universe, Prime Kira and Prime Bashir convinced Mirror Miles O’Brien, aka Smiley, and Mirror Benjamin Sisko to rebel against The Alliance. This kicked off a rebellion that lasted for several years. Kira and Bashir made it back to the Prime Universe and updated the crew of Deep Space Nine.
2371: Smiley Crosses Over and Abducts Sisko
In the episode “Through the Looking Glass,” Mirror O’Brien, Smiley, modified a transporter so he could cross over to the Prime Universe. He then downloaded key information from the Deep Space Nine computer, abducted Prime Sisko, and took him back to the Mirror Universe.
Once there, Smiley revealed that Mirror Sisko had died in a battle with The Alliance. However, Smiley didn’t want anyone to know about Mirror Sisko’s death. He was the leader of the Terran Rebellion and pretty much the only person keeping the effort together. Plus, he was supposed to convince his ex-wife, Mirror Jennifer Sisko, to betray the Alliance and join the rebellion.
Sisko agreed because he didn’t want the Mirror version of his wife to be killed by the Terran Rebellion. He manages to convince her to switch sides and gets back to the Prime Universe with the help of the rebels.
2372: The Seizure of Terek Nor
Just a year later, the Terran Rebellion was so powerful that they were able to take over Terek Nor, the ore processing station that served as a major base of operations for The Alliance. The episode “Shattered Mirror” revealed that the rebellion also managed to build a version of the USS Defiant based on plans Smiley had stolen from the Prime Universe. However, they couldn’t get the ship to function properly.
So, Mirror Jennifer crossed over to the Prime Universe to convince Prime Sisko to help them. She did so by kidnapping his son, Jake, and taking him back to the Mirror Universe. When Sisko followed and saw how desperate the rebels were to fight The Alliance, he agreed to help. He ended up piloting the ISS Defiant into a battle against The Alliance, winning the day for the rebels.
2374: The Attempted Reunification of Mirror Bajor
In the episode DS9 episode “Resurrection,” Intendant Kira sent a thief to the Prime Universe to steal one of the Bajoran Orbs. She believed that if she possessed an Orb, she could unify Bajor and become its rightful leader. Eventually, she also crossed over to the Prime Universe to see the plan through.
They were thwarted by Prime Kira and Prime Odo, who let them cross back over to the Mirror Universe.
2375: The Ferengi Incident
A year later, Prime Grand Nagus Zek used a multidimensional transporter to cross over to the Mirror Universe to establish business dealings in the Mirror Universe, as shown in the episode “The Emperor’s New Cloak.” However, upon his arrival, he was captured by The Alliance. They sent a mercenary, Mirror Ezri Dax, to inform Quark and Rom of the kidnapping and demand ransom.
When Quark and Rom transported over the Mirror Universe with Ezri, they were all captured by the Terran rebels. Quark and Rom tried to fulfill the ransom demanded by The Alliance while they were in Terran custody, but as it often does with Ferengi, only chaos ensued.
In a major turn of events, Ezri betrayed The Alliance and joined the rebels. The Terran Rebellion made another stand against The Alliance and the episode ended with the hint that they were victorious. However, the Trek canon is not clear on what happened in the Mirror Universe after 2375.
Star Trek Online Canon
The PC and console video game Star Trek Online (STO) continued the story of the Mirror Universe. Though STO is not “Star Trek” canon, it expanded the Mirror Universe in ways that fans have loved.
In the Star Trek Online canon, the Terran Rebellion defeated The Alliance in the early 2400s. This led to the new Terran Empire, which went back to its previous totalitarian ways. The STO canon introduced a war between the Mirror and Prime Universes, of which Admiral Leeta, the Mirror version of DS9’s Leeta, is a major player.
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