Spock ( mirror ) Spock was the / Vulcan hybrid first officer of the in 2267 . He was a logical being who was loyal to his captain , , and chose to warn him when he was ordered by the Terran Empire to kill him and take command if he did not launch an attack against the Halkan s in retribution for their refusal to negotiate with the Empire . Based on his captain ' s apparently erratic behavior , Spock correctly deduced that Kirk had actually been accidentally replaced by his counterpart from a mirror universe , and devised a means of returning Kirk , Scotty , McCoy , and Uhura to their original ship . Before Kirk left , believing that Spock would one day become captain of the " Enterprise " , he planted a seed of doubt about the inevitability of the Empire ' s collapse , asking Spock if violence was the only logical answer . Spock , as logical as his counterpart , was aware of the Halkan prediction that the Empire ' s subject peoples would revolt in approximately 240 years , and the Empire ' s defeat was a foregone conclusion . Kirk submitted that it was illogical of Spock to continue to serve an Empire destined to collapse , but Spock said the odds of one man bringing about peaceful change to the Empire were virtually insurmountable . Kirk revealed the existence of the Tantalus field , an assassination device that the mirror universe Kirk had used to eliminate his enemies , and urged Spock to ally the device ' s power with his own formidable intellect . Spock appeared intrigued , and promised to consider Kirk ' s words . ( ) As Kirk predicted , Spock later on became the captain of the " Enterprise " . Spock used the ship as a power base to accumulate influence , and eventually rose to become commander in chief of the Terran Empire . He instituted major reform s , turning the Empire into a more peaceful and less aggressive power . Unfortunately , Spock ' s reforms left the Empire unprepared to fight the united Klingon - Cardassian Alliance , who conquered the entire Terran Empire , enslaving the Terrans themselves as well as the Vulcans . ( ) Appendices . Background information . Mirror - Spock was portrayed by Leonard Nimoy . Nimoy , of course , also portrayed the prime - universe Spock . Both characters were identical , except that mirror - Spock famously wore a goatee beard : the " " imagery evoked by mirror - Spock ' s beard would later enter the larger cultural lexicon as a result of the character ' s portrayal in this episode . On featuring the mirror - universe Spock in , Ronald D . Moore commented , " " We were quite intrigued by the notion of using the Mirror Spock , but it never worked out for various reasons " " . In 1999 , rumors circulated that Leonard Nimoy would appear in as Spock . ( " Looking Ahead " , ) Nimoy ' s portrayal of mirror - Spock in " Mirror , Mirror " was the inspiration behind the name for the progressive - metal group " " . Apocrypha . In the novel " Dark Mirror " by Diane Duane , Jean - Luc Picard , masquerading as his mirror universe counterpart aboard the other ' s , briefly investigates Spock ' s history after his encounter with the primary universe Kirk . According to the official history , Spock succeeded , briefly , in becoming a powerful figure in Starfleet and the Empire , thanks to his own cunning and the use of the Tantalus Field , but his advocacy of less warlike policies eventually made him too many enemies . Both Spock and his father were discredited , then convicted of treason and executed . As the novel predates the establishment of the history of the televised mirror universe , these events are contradicted by the history related by to her counterpart in " Crossover " , as well as the appearance of the mirror universe ' s Sarek in . Spock appears in the novella " " , which was subsequently expanded into the full length novel of the same name . Several days after the events of " Mirror , Mirror " , Spock is depicted as murdering the mirror Kirk and thereby assumes the captaincy of the ISS " Enterprise " . He later marries Marlena . The story focuses on Spock ' s rise to the leadership of the Terran Empire in 2277 , his rule and the events leading to its transformation into the short - lived Terran Republic and the subsequent conquest of Earth and Vulcan by the Alliance in 2295 .