Anton Karidian was an alias assumed by Governor Kodos, also known as "Kodos the Executioner", after a massacre on Tarsus IV in 2246. Living as such, Anton Karidian was a traveling actor with the Karidian Company of Players, the star and director of this troupe of itinerant actors. He was also the father of Lenore Karidian. Ultimately, however, he was killed by her. (TOS: "The Conscience of the King")
In 2257, his Karidian Company of Players was sponsored by the Galactic Cultural Exchange Project. For the next nine years, Anton Karidian toured with this company as they visited official installations.
In 2266, the Karidian Company visited Planet Q. One of the residents of that world was Thomas Leighton, who recognized Karidian as Kodos. He asked James T. Kirk to investigate, as Kirk was one of nine people who had actually seen Kodos. After a series of murders and attempted murders, Kirk was convinced that Karidian was Kodos and was killing witnesses to cover his identity. In actuality, it was Lenore who had been committing the crimes. When Lenore confessed this to him, Karidian was horrified that the past that he spent years living down had instead poisoned her to become a remorseless serial murderer determined to protect him.
At that confession, Kirk overheard it and confronted the both of them. In desperation, Lenore tried to flee with her father onto the stage and when she saw that they were trapped, she grabbed security guard Harrison's phaser to threaten Kirk and his ship. Further aggrieved to see his daughter was without a doubt utterly insane, Karidian jumped in the line of fire as she fired at Kirk, killing him. (TOS: "The Conscience of the King")
Anton Karidian was played by Arnold Moss.
In ultimately unused dialogue from the final revised draft script of "The Conscience of the King", Kirk made arrangements regarding Anton Karidian staying aboard the USS Enterprise, Kirk privately telling Spock, "Karidian is somewhat of a hermit. Pass it on to all hands… he's not to be disturbed."
Later in the teleplay, Karidian approached Spock and McCoy at night, in a corridor aboard the Enterprise. His presence there seemed somewhat suspicious, as he came up to the pair of officers from behind them, interrupting a conversation they had been having about the possibility of Karidian being Kodos. The script's stage directions remarked that Karidian was to be "in a dressing gown, his white hair framing his face, his head like a lion's, proud and aloof… but he seems a little… apologetic." Uttering polite apologies, he claimed he had lost his way aboard the ship and that he liked to take walks when everyone was asleep, as he felt he could rest better by doing so. As Spock told him the corridor they were in was one of the restricted areas of the ship, Karidian soon left, leaving Spock to wonder how much of the previous discussion he had overheard. This scene was never filmed due to time constraints. (These Are the Voyages: TOS Season One, p. 296)
In another unused scene from the same script, a distraught Karidian was pacing in his quarters aboard the Enterprise, the teleplay's stage directions commenting, "Karidian's composure is not that of the acclaimed actor confident in his talent and the homage of the civilized universe. Instead, we see a harried man, pacing nervously." After Lenore Karidian entered, he asked where she had been, though she merely replied she was with him now. He was calmed by her, and eased gently down on his bed by Lenore, as it was her recommendation that he have a nap. This scene was filmed, but cut from the finished episode due to it running too long. (These Are the Voyages: TOS Season One, p. 294)
When later visited in his quarters by Kirk (in a scene which does take place in the final version of the episode), Karidian was characterized in the script thus; "Karidian, present, is wearing a dressing gown which resembles a kingly robe and looks a dominant and distinguished figure." The next sentence reinforced the notion of him looking "kingly".
During casting, someone recommended that an actor with a powerful delivery and a strong sense of drama be chosen to play the role of Karidian. Casting Director Joseph D'Agosta and "The Conscience of the King" Director Gerd Oswald were jointly responsible for selecting Moss. (The Star Trek Compendium, 4th ed., p. 44) The actor himself stated, "The character was called Anton Karidian or Kodos, either one or the other [....] You never knew which because he was either a man from some other planet who had killed 8,000 people or an actor – a Shakespearean actor who traveled from planet to planet to entertain." Moss also recalled part of the preparations which the role required, commenting, "I remember a 6 a.m. makeup call when I didn't have much makeup." (Starlog, issue #130, p. 72)