Goma worms are the actual cause of the "zombie" plague that desecrated Ebera. They were released when thieves broke into a tower the long-dead wizard Kel Jerud had made; the wizard had created the goma worms and set them to be unleashed should anyone enter the tower.
After the plague had spread, a number of people with the ability to keep themselves from succumbing to the gomas' infectious bloodlust tasked themselves with guarding their fallen kingdom. When a group of these Ebera guardians met Jason, Rachel, and their group, they threatened to keep them stuck in Ebera so the plague would not spread outside the border. The guardians threatened the group with tiny sacks of goma worms, which would have been used to infect the group. If it had not been for Rachel's quick-thinking use of Edomic, they might have ended up infected. Most of the group made it through Ebera safely after this, despite being chased by hordes of goma-infected people.
During this trip, Nedwin secretly collected a sample of goma worms. Later, when he was mortally wounded by the throne-usurper Copernum, he swallowed this sample. After dying, he woke up again thanks to the goma worms, which heightened his senses in some ways (as well as gave him a lust for blood, which he never gave in to). This second chance gave him a temporary amount of time to finish what he had started with Copernum. After killing the evil chancellor, Nedwin lay down in a roaring fire, finally dying for good, to ensure the goma worms inside him would be killed and prevent the plague from spreading.