Born Cardassian, this female Obsidian Order agent was surgically altered to appear Bajoran and infiltrate a Maquis cell commanded by former Starfleet officer Chakotay. A good friend of the Starfleet dropout B'Elanna Torres, she joined the cell after Chakotay's approval and soon became his lover.

Swept into the Delta Quadrant when the Caretaker Nacene pulled her ship and the U.S.S. Voyager there, Seska was among many who were merged into the crew on the starship. Seska was among those involved in he early weeks of friction with the merged crews, supporting Torres in her bid for chief engineer against Tom Carey and helping plot to take Sikarian spatial trajector technology against Janeway's orders. Even so, she eventually drifted away from both friend and lover as the two assimilated into Voyager's command structure.

Frustrated at Janeway's leadership that thwarted both getting home and building alliances, Seska finally revealed her true nature after having been caught stealing transporter technology to the Kazon-Nistrim. She escaped to become the consort of the Nistrim first maje, Culluh, and was the power and brains behind his brief rise to glory despite her frustration at keeping her ambitions in check publicly, thanks to Kazon male chauvinism.

Mindful of Chakotay's anger at being fooled by her while in the Maquis, Seska grew adept at manipulating him and Voyager to benefit the Kazon. She continued to toy with Chakotay's emotions as if unsure herself about her feelings for him and, during one mission in which he was kidnapped even impregnated herself with his DNA. Seska, who allowed her true Cardassian appearance to re-emerge while among the Kazon, was shocked to learn months later that her infant son was not Chakotay's but Culluh's instead, having told her maje that the human raped her while in his crew.

Ironically, Seska died aboard her old starship ca SD 50037, as Culluh's short-lived conquest of the prize vessel came to an end. Leaving her behind, he escaped with their baby boy.

Before leaving the Voyager ca. SD 48658, she had reworked Tuvok's abandoned "Insurrection: Alpha" holo-scenario so it would backfire on him with deadly results, long after her actual demise.