Catta Dionize was a subordinate of Madame Travia Chan, who headed up the Atrivis Resistance Group during the early rebellion against the Galactic Empire. From Generis Station in 5 BBY, Dionize penned a letter to Senator Mon Mothma on Chan's behalf. This letter communicated the Resistance Group's agreement to collaborate with Mothma's Alliance to Restore the Republic, citing the Galactic Empire's victory against resistance forces on the planet Mantooine earlier that year as a situation the partnership aimed to avoid in the future. This correspondence was kept as part of the Rebel Files, a collection of physical records documenting the Alliance's history.
The character of Catta Dionize initially appeared in Star Wars: The Rebel Files, a reference book authored by Daniel Wallace and released in 2017.