Marta was a 23rd century Orion woman, a former Orion slave girl who gained a reputation as a heroine, legendary politician and murderess, before her fall from power and captivity in the Elba II penal colony.
Beginning her career as an Orion slave on an Orion colony world, Marta seduced, schemed, and quietly murdered a path to the top. She came to the largest casino on planet Rigel II, where she became the star attraction, and later, the manager. She found fame performing in Shakespearean drama, where her beauty and inventive costuming made her plays popular holotapes across the quadrant.
On Rigel II, Marta continued her efforts to increase her power and expand her network. She seduced, spied for, and sometimes betrayed, officers of Starfleet, the Andorian Defense Force and the Klingon Empire.
When the ruler of Palmyra II gambled away his fortune at her casino, she married him and seized the planet for herself. To dismantle the world's corrupt bureaucracy, Marta famously invited the worst offenders to a private dinner and performance of Macbeth and poisoned the wine. (Decipher RPG module: Narrator's Guide)
Marta later became the lover of the Romulan centurion Vonath, and the pair launched an attempted conquest of Canopus IV. But Marta was captured by Starfleet and she was sentenced to life imprisonment on the penal colony of Elba II in 2266. Vonath and the Orion Syndicate were both considered as potential architects of a hypothetical plot to free her. (Decipher RPG modules: Narrator's Guide, Worlds)
By 2269, she was apparently diagnosed as suffering "paranoia with delusions of reference" (though this might have been made up by Garth of Izar). She claimed to be the most beautiful woman on the world (albeit the only one), a poet, a painter, and a dancer. However, her poetry was plagiarized from Shakespeare and other writers.
Following Garth's escape, she fell in with his band of escaped patients as they seized control of the colony. She initially tried to warn James T. Kirk, possibly as part of their initial ruse. At Garth's banquet, she sang her false poetry and danced. Though she fawned over Garth, she flirted with Kirk and pleaded for his life, which angered Garth and caused him to threaten her; she feared for her own life.
Marta later treated Kirk, and claimed to have released Spock from imprisonment, or thought she did, by telling a lie to a guard who desired her. However, she was unwilling to go against her leader, Garth. She decided she loved Kirk, so much so that she could not bear to lose him, so she attempted to kill him to save him from Garth. Kirk fought her off, and Spock (or rather, Garth) knocked her out with a Vulcan nerve pinch.
In Garth's coronation ceremony, he named his "beloved" Marta his consort—then had her dragged out into the poisonous atmosphere of Elba II. Shortly before she could die from the poison, he blew her up instead as a demonstration to Kirk. (TOS episode & Star Trek 5 novelization: Whom Gods Destroy)
- The novelization of Whom Gods Destroy doesn't say that Marta is Orion, and instead has Kirk wonder if Marta is of distant Vulcan or Romulan descent.