The Mol'leaj system was located in the Expansion Region and the Slice, within grid square O-14 of the Standard Galactic Grid. It was ruled by Regent Solculvis, who controlled multiple worlds in territory neighboring that of King Grevoth Prana IX of the Kaboryth cluster. By around 34 ABY, Solculvis' regency was independent and did not enjoy a favored status with the New Republic.
Around that year, the New Republic Sector Rangers discovered the cargo starship Sketter's Quarrel dead in space. The vessel, which had been destined for Solculvis, had been transporting several exotic creatures the private ownership of which was illegal, and later around that same year, information from the Rangers' file on the case, which mentioned Solculvis' regency in the Mol'leaj system, was published in the book Scum and Villainy: Case Files on the Galaxy's Most Notorious, which was authored by New Republic Police Commissioner Exantor Divo.
The Mol'leaj system was simultaneously first mentioned in the December 18, 2015 Alan Dean Foster's adult novelization of the sequel trilogy film Star Wars: Episode VII The Force Awakens and the reference book Star Wars: The Force Awakens: The Visual Dictionary by Pablo Hidalgo. In the novelization, the scene where Han Solo tells Rey and Finn that he is transporting three rathtars aboard the freighter Eravana features a different dialogue than the one present in the film, with Solo mentioning King Grevoth Prana IX's rivalry with the regent of the Mol'leaj system.