Aplooine, found in the Outer Rim Territories' Grumani sector, was a world whose surface was largely covered by ash. Although only a few stable locations for landing existed on its mountaintops, this planet played a role in the early exploration of the surrounding space during the Kymoodon Era. In the millennia that have passed since that time, Aplooine has continued to be inhabited by colonists.
Within the Trailing Sectors region of the Outer Rim Territories, Aplooine existed as a terrestrial world within the Aplooine system, which itself was a component of the Grumani sector. Positioned along the Duros Space Run hyperspace route, it served as a link between the Sanrafsix and Verdanth systems. The surface of Aplooine was characterized by a layer of black ash, reaching depths of up to three hundred meters, with only a sparse distribution of stable landing sites located on its weathered mountains. The atmosphere of the world was unbreathable.
During the Kymoodon Era, spanning from 15,000 BBY to 12,000 BBY, a small area of space that had been explored by the Galactic Republic expanded around Aplooine and Heptooine in the southern part of the galaxy. Aplooine's location on the Duros Space Run allowed it to function as a port for colonists for many millennia after that time. By the period between 12,000 and 11,000 BBY, according to the Galactic Standard Calendar, the world had become part of the Republic, despite its location in Wild Space. In 1032 BBY, Jedi Master Vannar Treece made a brief reference to Aplooine within a cartographical survey and field report concerning the Grumani sector.
Aplooine was initially referenced in The Essential Atlas, a reference book from 2009 written by Daniel Wallace and Jason Fry. This book placed it in grid square M-17. However, a 2010 StarWars.com article titled Essential Atlas Extra: The Knight Errant Gazetteer, co-written by Wallace, Fry, and John Jackson Miller, instead positioned it in grid square N-17, as designated by The Essential Atlas. This placement was subsequently confirmed by the Online Companion to the book on StarWars.com.