Jarnollen, a world abundant with tropical jungles and overgrown vines, existed near Ord Mantell within the bounds of the Mid Rim.
Jarnollen hosted an Imperial training facility not long after the Battle of Yavin. Unaware of the Empire's presence, Luke Skywalker and Leia Organa were sent to the planet with the intention to assess its suitability as a potential new Rebel base. They discovered the Imperial occupation just as an Imperial patrol stumbled upon their landed vessel, destroying it with proton grenades and deploying all available forces to hunt down the Rebels. The pair spent the majority of the night and the following dawn evading an Imperial AT-AR, before Han Solo and the Millennium Falcon arrived to rescue them.
The original comic did not provide a name for this planet. However, Pablo Hidalgo's material for the Star Wars Adventure Journal, titled "The Jarnollen Expedition", would have given the planet its name, but the Journal was discontinued. Ultimately, the name was officially established in 2008 within The Complete Star Wars Encyclopedia, which Hidalgo co-authored.