Marci Sertim was a Human female mercenary attached to a civilian security force guarding a hyperbaride synthesis plant on the planet Marca, along with her twin sister Darci and older sister Gayle. Gayle was killed by Vost Tyne, who claimed her death to be the work of the Alliance to Restore the Republic. Marci and Darci went on to harbor a strong hate towards the Rebellion until they came across recently captured Rebel agents. The Rebels revealed the truth behind Gayle's death and the sisters decided to help them escape and get revenge on Tyne. Tyne found out and had the two arrested, imprisoning Marci in the plant's holding cells. The Rebel agents were able to free her and she set about self-destructing the facility by overloading the plant's hyperbatteries. Marci headed for the plant's landing bay intending to steal a starship to get off-planet. She wanted to wait for Darci as long as she was able to, but she would have left if her sister didn't arrive on time. Marci was a cold-blooded mercenary at heart, caring for nobody except herself and Darci.
- Planet of the Mists (First appearance)