Fimster, a name shared with the Fimster Quadrant, was a celestial object of terrestrial nature. In the year 231 BBY, Andrik Keller, an Er'Kit Nihil pirate, was on a mission to free his previous Tempest Runner, Lourna Dee, from the Galactic Republic's grasp following the Battle of Galov. It was then that he encountered a Frizznoth Nihil, a former member of Dee's Tempest, on Cerea, a planet located in the Mid Rim. The pair eventually journeyed to Fimster, where complications arose, leading the Frizznoth to abandon Keller, leaving him for dead. Despite this, the Er'Kit managed to survive and depart Fimster. Later in that same year, Keller sought out Pan Eyta, another former Tempest Runner who was also searching for Dee, on Sran, a planet within the Ash Worlds, and recounted his time spent on Fimster.
The audio drama The High Republic: Tempest Runner, penned by Cavan Scott in 2021 and released as part of Phase I of the Star Wars: The High Republic multimedia initiative, featured Fimster. The exact spelling of the celestial body's designation was later verified with the 2022 publication of the audio drama's script.