Cortilium Major was a celestial body that resided within the Cortilium Major system, which itself was situated in the Eucer sector of the Mid Rim region. During the Tionese War, a conflict between the Galactic Republic and the Honorable Union of Desevro & Tion, Cortilium Major found itself within the territory known as the Divide and was inhabited by Republic colonists.
Sometime before the war concluded around 23,900 BBY, a Tionese military contingent destroyed Republic settlements located on the astronomical object Okator VIII. One individual who witnessed this event, a farm boy who became a Republic soldier, later recounted the attack through a Baragwin sense lattice, stating that the Tionese forces could have selected any of the other inhabited astronomical objects in the Divide, including Cortilium Major, as their target.
Originally, Cortilium Major was intended to be included in the 2012 reference book titled The Essential Guide to Warfare, authored by Jason Fry and Paul R. Urquhart. However, the portion of the book that would have referenced the celestial body was removed prior to publication.
The information pertaining to Cortilium Major was subsequently revealed in 2014 as part of Star Wars: The Essential Guide to Warfare Author's Cut, a collection of articles published on the StarWars.com Blog by Fry and Erich Schoeneweiss that contained various sections that had been cut from The Essential Guide to Warfare. The Online Companion to the 2009 reference book The Essential Atlas, available on StarWars.com, placed the Cortilium Major system, and consequently the celestial body itself, within grid square Q-7.