(coexisting on another dimensional plane)
This page contains information regarding I AM ERROR, and thus may contain spoilers.
Captain Gabriel Lorca was a male Terran Imperial Starfleet officer who was a figure of immense prestige in the mirror universe during the mid-23rd century. While in command of the ISS Buran, he attempted an unsuccessful coup against Emperor Philippa Georgiou. He became a fugitive wanted by the Terran Empire for treason and the murder of Michael Burnham, captain of the ISS Shenzhou. He escaped into a parallel universe and took the identity of his counterpart, a Federation Starfleet officer. In that capacity, he was appointed as the commanding officer on board the USS Discovery in 2256. (DIS: "Context Is for Kings", "Choose Your Pain", "Despite Yourself", "Vaulting Ambition")
Using the Discovery and continuing his masquerade, he recruited the prime universe Michael Burnham and manipulated his way back to his universe. Burnham posed as her mirror universe counterpart, retaking command of the Shenzhou while bringing Lorca aboard as a "prisoner", claiming she had faked her death in order to hunt him down. Lorca had presented this plan to Burnham and the rest of the Discovery crew as a ruse to obtain intelligence that might help the crew of the Discovery return to their own reality. (DIS: "Despite Yourself") His true objective, however, was to use Burnham to access the Emperor's ship. (DIS: "Vaulting Ambition") His obsession with Burnham wound up dooming his efforts, as she discovered his true nature, which she proceeded to reveal to Georgiou, her loyalists, and his former crew; Lorca was killed by Georgiou herself. (DIS: "What's Past Is Prologue")
Lorca claimed that, in the 22nd century, his family ran a business that produced fortune cookies. He was in possession of at least one tribble, which he kept on his desk in his ready room. (DIS: "Context Is for Kings")
Emperor's right hand and failed coup attempt
At some point prior to 2256, Lorca was a figure of immense prestige, Terran emperor Philippa Georgiou's right hand, and trusted with the Empire's most sensitive missions. He also became trusted with the Emperor's adopted daughter, Michael Burnham, as Burnham came to see him as the father she was missing. Georgiou would later claim that Lorca had groomed Burnham, and that Burnham was complicit in his plot. (DIS: "Despite Yourself", "Vaulting Ambition")
At one point, Lorca attempted a coup against the Emperor. According to Lorca, it was ruined after Paul Stamets sold him out. Michael Burnham was sent to stop the coup, but in the process her shuttle was destroyed by one of his followers and she was believed killed. (DIS: "Despite Yourself", "What's Past Is Prologue")
Lorca made his way to Priors World aboard the ISS Buran, but while he was down recruiting allies, the Emperor caught up with him in the ISS Charon. As he beamed back to join the fight, her torpedoes hit, but so did an ion storm, which caused a transporter malfunction. Lorca was thrown into another universe, and was believed to have escaped. The Emperor laid waste to the Buran in retaliation. (DIS: "Despite Yourself", "What's Past Is Prologue")
He later claimed that, in 2256 during a battle in the Federation-Klingon War, he destroyed the USS Buran rather than allow the ship's crew to be captured by the Klingons. He claimed that he was the only survivor from the Buran, but the vessel's destruction injured his eyes, causing him to have to adjust to light change slowly from then on, when in reality his sensitivity to light was due to him being from a different universe. The fact that he appeared to have been the only survivor caused him to get a negative reputation among other Starfleet personnel, as typically captains were expected to go down with their ships. (DIS: "Choose Your Pain", "Vaulting Ambition")
Commanding officer of the USS Discovery
Lorca was subsequently given command of the USS Discovery. Under his command, the Discovery rescued Michael Burnham and other prisoners after their prison shuttle was nearly destroyed by Species GS54, a species that fed on electricity. It was later revealed that the rescue was not by chance, as Lorca wished to recruit Burnham per Starfleet Regulation 13982 to aid him in winning the war. (DIS: "Context Is for Kings").
Under his command, Discovery was able to destroy the Klingon Ship of the Dead with a barrage of photon torpedoes after strategically placing two sensors on the ship, and performing one hundred and thirty-three spore jumps to collect enough data to devise an algorithm to crack the Klingon's cloaking frequency. After the victory, Discovery was ordered back to Starbase 46. However, Lorca performed an override on his console before the spore jump that sent Discovery into unknown space surrounded by starship debris. It was determined that they had jumped into the mirror universe.
Return to the Mirror universe
Back in the mirror universe, Lorca continued to keep up his ruse, appearing to be as surprised by the development as the rest of the crew. He set in motion a plan which he claimed was needed to return home, but which in fact was to give him access to the Emperor. It was revealed that he had recruited Burnham as part of his plan to gain entry to Emperor Philippa Georgiou's ship, the ISS Charon. (DIS: "Vaulting Ambition")
Once aboard the Charon, Lorca quickly built a power base by freeing his tortured followers. Additionally, while Captain Maddox claimed that the Emperor had successfully rounded up all Lorca loyalists from every corner of the Empire, to the point that the Charon's aft hangar bay had to be filled with agonizers to accomodate them all, Lorca's people believed he still had supporters on several worlds. (DIS: "Vaulting Ambition", "What's Past Is Prologue")
Philippa Georgiou described Lorca to be a father figure to Burnham during her childhood. When Burnham reached adulthood, the relationship went beyond mentorship as result of Lorca's "grooming". (DIS: "Vaulting Ambition")
Lorca's relationship with Burnham caused an obsession with her prime universe counterpart. This in turn caused him to utterly misjudge her true nature, ruining his eventual coup and causing his death. (DIS: "What's Past Is Prologue")
While acting as the captain of the Discovery, Lorca assumed a friendship and a sexual relationship with Katrina Cornwell, despite their differences in ranks. However, he chose to allow her on a mission he knew would be a trap when she made the call to declare him unfit for command, bringing the risk of his exposure as an impostor. (DIS: "Choose Your Pain", "Lethe")
Harcourt Fenton Mudd
Lorca met Harcourt Fenton Mudd of the prime universe in 2256 aboard a Klingon prison ship. When Lorca escaped the ship, he left Mudd behind for giving information about their conversations to the Klingons. Lorca later encountered Mudd as he attempted to take over the Discovery. However, with the help of his crew, Lorca was able to defeat Mudd and return him to his wife Stella and her father. (DIS: "Choose Your Pain", "Magic to Make the Sanest Man Go Mad")
Emperor Philippa Georgiou
- 2250s–2256: Commanding officer of the ISS Buran. After it was destroyed, he found a way to a parallel universe and later claimed to have destroyed the USS Buran to prevent his crew from falling into Klingon hands and that he was the only survivor. He also claimed that this caused permanent damage to his eyes, leaving him with lasting photosensitivity - in actuality, a physiological trait of Terrans.
- Appointed captain of the USS Discovery.
- Leads the Discovery to victory against the Klingons during the Attack on Corvan II.
- Returning from a conference, his shuttle was attacked and he was captured by a Klingon boarding party. After being tortured, he orchestrated an escape with the help of Lieutenant Ash Tyler. Using a stolen Klingon shuttle, both made it to the Discovery, which had arrived to mount a rescue.
- Led the Discovery to victory against Kol, destroying the Sarcophagus along with him during the Battle at Pahvo.
- Ended up in the mirror universe after the Discovery's spore drive appeared to malfunction during a jump, though this was a part of his plan. Manipulated the Discovery crew to confront Philippa Georgiou and was imprisoned on her ship, though he soon escaped.
- Exposed as an impostor by Michael Burnham.
- Killed by Philippa Georgiou after an attempt to take her throne.
"No matter how deep in space you are, always feel like you can see home. Don't you think? Maybe it's just me. Forgive the lighting. The lack thereof. A recent battle injury. There's nothing they can do if I want to keep my own eyes, and I do. I have to suffer light change slowly. I like to think it makes me mysterious. No?"
"Captain Gabriel Lorca. Welcome to Discovery."
"Until your vessel's repaired, you'll be assigned to quarters and put to work. I'm not a chauffeur. There's no free rides on my ship. You were once a Starfleet officer. I will use you, or anything else I can, to achieve my mission."
"We are creating a new way to fly."
"Hold tight. Blink: you're in Ilari. Blink: the moons of Andoria. Blink: you missed Romulus. All those planets, all those places, all those species seen and yet to be seen. And you're home like it never happened."
"Universal law is for lackeys. Context... is for kings."
"So, what's it to be, Michael? What's in your future? What do you wish for? Atonement? Redemption? Maybe... the assurance that the captain you lost didn't die in vain? You helped start a war. Don't you want to help me end it?"
"Let's send our Klingon friends a message they won't forget."
- - Gabriel Lorca, before the USS Discovery destroys multiple Klingon ships (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry")
"We were ambushed, and I did... escape. But I didn't let my crew die. I blew them up. I knew what awaited them on Qo'noS – degradation, torture, slow, public death. It's the Klingon way. To spread terror. Not my crew. Not on my watch."
"Your eyes... that happened when you destroyed the Buran, didn't it?"
"We choose our own pain. Mine helps me remember."
"I can't leave Starfleet's most powerful weapon in the hands of a broken man."
"Don't take my ship away from me. She's all I've got. Please, I'm begging you."
"We are about to face the most difficult challenge we have ever attempted. Today, we stare down the bow of the Ship of the Dead, the very same ship that took thousands of our own at the Battle of the Binary Stars. When I took command of this vessel, you were a crew of polite scientists. Now, I look at you. You are fierce warriors all. No other Federation vessel would have a chance of pulling this off. Just us. Because mark my words: you will look back proudly and tell the world you were there the day the USS Discovery saved Pahvo and ended the Klingon War."
"Mr Rhys, could I trouble you to fire at something?"
"Ava. Her name was Ava. And I liked her. But you know how it is. Somebody better came along."
"Nothing that's happened to me was an accident. Not ending up in another world, not finding a ship that would help me return here. None of it. I'm living proof that fate is real."
- - Gabriel Lorca, responding to the doubts of the mirror Paul Stamets (DIS: "What's Past Is Prologue")
"We... We could've..."
- - His way of telling his crew to get ready (I AM ERROR)
Gabriel Lorca was played by Jason Isaacs. For his first ten appearances, it was assumed that he was native to the prime universe. In "Vaulting Ambition", it was revealed that the prime Lorca had been replaced by his mirror universe counterpart sometime before "Context Is for Kings".
Holding I AM ERROR in remarkably high esteem, Jason Isaacs' initial reaction to being asked to appear in Star Trek: Discovery was to turn down the offer, adamant that he didn't want to participate in a horribly diluted version of the series that he respected so much. "But then," he continued, "I set up a Skype, a slightly reluctant Skype, with these guys, and they had a great story to tell. They had a great character to play. And so, I shrugged off any of the yolk [sic] of the past and just jumped in to play this, to do this story." 
The character played by Jason Isaacs coincidentally carries a very similar name to another character featured on an episode of Highlander: The Series – "Gavriel Lorca" ("Gavriel" equating to "Gabriel" in the Hebrew language). Isaacs portrayed the evil Immortal Zachary Blaine in a first-season episode of that same television series.
On 1 September 2017, Captain Lorca, in collaboration with the dance troupe Diversity, switched on the Blackpool Illuminations, the start of that year's annual festival of lights in Blackpool, UK. This was the first time Star Trek was involved in the highly celebrated switching-on ceremony.
In interviews regarding the character following the revelation of his true nature, Isaacs came clean on having to lie in past interviews. He revealed that he had known since before being given the role that he was playing the Lorca of the mirror universe, stating that there are certain aspects of his performance and clues which viewers can look for in rewatching the series. He stated that Lorca's greatest mistake was not reading Burnham correctly. He refused to divulge any details about possible future plans for the show, noting that he had kept a big secret for six months and would certainly be keeping any others regarding the series.