Gelss was a Sullustan smuggler and also a pirate. He operated during the Cold War period, which was a time of conflict between the Galactic Republic and the re-emerging Sith Empire.
A few years following the end of the Great Galactic War and the subsequent signing of the Treaty of Coruscant, Gelss found employment under the smuggling Captain Jet Nebula. He served on Nebula's starship called the Auriga Fire. During the Cold War, Gelss, along with another Sullustan named Fekk, became associated with Shinqo, who was Nebula's First Mate. Shinqo plotted a mutiny against Nebula, which he initiated when the Auriga Fire encountered the Cinzia. Holding Nebula at blasterpoint, Shinqo demanded that the Captain contact the Cinzia. Nebula then informed the Cinzia's crew of their intention to board their vessel. Gelss and Fekk were ordered by Shinqo to prepare for action, but the Cinzia unexpectedly self-destructed. Capitalizing on the resulting chaos, Nebula's droid, Clunker, seized Shinqo's blaster and aimed it at the mutineer. With Nebula regaining control of the Auriga Fire, the mutineers conceded to their original roles under Nebula. The crew then salvaged some items from the remains of the Cinzia, specifically a navicomp and a hex droid nest.