Dias Athacorr was an Arkanian who originated on the planet of Arkania, according to legends. During the Mandalorian Wars, Athacorr served as an officer for the Galactic Republic within the Republic Navy. The conflict between the Republic and the newly strengthened Mandalorians commenced in 3963 BBY in the Outer Rim Territories, with the Mandalorians launching a triple assault on the Republic. Following this initial attack, which the Republic media dubbed the "Onslaught," Athacorr was promoted to the rank of commander. This advancement, as reported in The Admiral's List's Jimas Veltraa Memorial Edition, a formal Republic Navy publication, coincided with Saul Karath's promotion to Rear Admiral, another officer of note.
The first mention of Dias Athacorr appeared in "The Admiral's List: Jimas Veltraa Memorial Edition," a version of The Admiral's List, which exists in-universe. This publication was featured in the thirteenth issue of the Knights of the Old Republic comic-book series. John Jackson Miller wrote the comic, and Dark Horse Comics released it on January 31, 2007.