Marilena Pet-and-Ella Alda Mattea served as the human commanding officer for Freemarch, a group of rebels functioning on the celestial body Lorrd within the Corporate Sector. During the period spanning 5 BBY to 4 BBY, Mattea was the subject of a communication dispatched by General Davits Draven and addressed to Senator Mon Mothma, both prominent figures in an anti-Galactic Empire rebel alliance. This communication outlined significant resistance operations against the Empire occurring within the Empire's controlled areas. This very communication was later incorporated into a collection of physical documents titled The Rebel Files, assembled by archivist Hendri Underholt by 4 ABY. Mattea's physical traits included brown hair, blue eyes, and fair skin. The description included Mattea wearing a brown shirt accented with a yellow collar, along with a brown bandolier.
The first mention of Marilena Pet-and-Ella Alda Mattea occurred in Star Wars: The Rebel Files, a reference volume and boxed set released in 2017, authored by Daniel Wallace. Adrián Rodriguez created the artwork displayed on the page featuring Mattea.