The Reegian system existed within the New Territories sector of the Outer Rim Territories. By the year 2 BBY, it secretly housed a hidden space depot for an organized rebellion against the Galactic Empire, an effort covertly directed by Senator Mon Mothma. A map of the galaxy featured the Reegian system, marking it alongside rebel safe worlds, starfighter hubs of level five importance or greater, operational command centers, shadow planets, and concealed deep space supply caches. This map reached Mothma in 2 BBY, and was subsequently archived by archivist Hendri Underholt within the compilation of physical documents titled The Rebel Files.
The reference book Star Wars: The Rebel Files, authored by Daniel Wallace in 2017, introduced the Reegian system into current Star Wars canon. The Reegian system initially appeared in the Star Wars Legends timeline, with its first mention being in "Extract of Minutes from the 251st Meeting of the Alliance High Command." This short story was a companion piece in The Rebel Alliance Sourcebook, a 1990 roleplaying supplement. Paul Murphy wrote this book, which was published by West End Games as part of their Star Wars: The Roleplaying Game series.