The Excalibur survived an attack by the Borg during a night shift sometime prior to late 2368. Several members of the crew, including Wilkarah, were assimilated in the encounter. As a Borg drone, she was a member of Seven of Nine's unimatrix, where she was assigned the designation of Three of Nine, Auxiliary Processor of Unimatrix Zero One.
In 2368, a Borg sphere crashed on Planet 1865-Alpha, an uninhabited planet in the Delta Quadrant. The drones Two of Nine, real name Lansor, Three of Nine, Four of Nine, real name P'Chan, and Seven of Nine, were the only survivors. Their link to the Borg Collective was temporarily severed, allowing them to regain their individualities.
P'Chan, Lansor, and Marika intended to hide so that they would not be found when the Borg came to retrieve them. They went their separate ways. However Seven of Nine, terrified of her new-found individuality, hunted each of them down and forcibly interfaced with each of them using her assimilation tubules. She caused the left parietal lobes of their brains to be transformed into interlink nodes that linked them together in an ad hoc collective, then erased the act from their memories. She then led them back to the crash site, where the Borg retrieved them.
Eventually, P'Chan, Lansor, and Marika escaped the Collective, but could not break their ad hoc link, and thus were denied true individuality. In 2376 they sought out Seven of Nine on the USS Voyager in the hopes that she could help them, and discovered her responsibility for the link. While retrieving their memories, P'Chan, Lansor, and Marika fell into a coma.
The Doctor, Voyager's holographic chief medical officer, found that to wake P'Chan, Lansor, and Marika from their coma they needed to be reintegrated into the Borg Collective. The only way to wake them up was to break the link by removing their interlink nodes. However, this would kill them within a month. Seven and The Doctor decided to perform the procedure, knowing that they would prefer a short life as individuals to rejoining the Borg Collective as drones. Marika, glad to be aboard a Federation vessel again, decided to spend her remaining time aboard Voyager. (VOY: "Survival Instinct")
Background information Edit
Marika Wilkarah was played by Bertila Damas.
Her capture by the Borg is seen in the short story "Making a Difference" in the New Frontier anthology No Limits, but does not explain her survival of the destruction of the Borg cube. "Making a Difference" erroneously places Marika's assimilation in 2369, the year after she was seen as a drone in "Survival Instinct".