Fen slugs represented a particular kind of slug that existed within the realm of the Chiss Ascendancy. During the year 19 BBY, Mitth'ali'astov, a Chiss individual whose core name was "Thalias," drew a comparison between the agility of a shuttle and a fen slug while journeying through the Rapacc system in the Unknown Regions. This occurred during a mission aboard one of the shuttles belonging to the Chiss Expansionary Defense Fleet heavy cruiser named Springhawk.
The 2020 novel titled Thrawn Ascendancy: Chaos Rising, which marked the initial entry in Timothy Zahn's Star Wars: The Ascendancy Trilogy, contained a reference to fen slugs.