Sludge salamanders represented a species originating from an unmapped swamp planet situated within Wild Space; the Graf family briefly designated this planet as Graf-World. During an endeavor by Milo Graf, the Grafs' youngest child, to ensnare an ash-rabbit that he located within the swampy terrain, the family's droid, CR-8R, inquired whether the creature being pursued by Graf was a sludge salamander or a horned billipede.
The initial mention of sludge salamanders occurred within the pages of the novel titled Adventures in Wild Space: The Escape, authored by Cavan Scott and published during the year 2016.