Cymotes were purple parasitic creatures that were thought extinct for eons by the time of the Galactic Civil War. Considered a nightmarish and horrifying threat, they laid eggs within the mouth of a living host and ate their way out of the host when hatched. Because their bodies were delicate under their shells, they were edible. The rogue archaeologist Doctor Chelli Lona Aphra learned of them and claimed it was surprising they were popular in the dinnerware of the ancient Merelithic culture. In 3 ABY, a number of cymotes, despite their supposed extinction, were present aboard the Opal Empress as it transported Ebann Drake to what he described to his cousin Domina Tagge as an incredible opportunity.
Sometime later, Aphra and the smuggler Sana Starros were sent by Tagge to locate Drake and discover what the opportunity was. By the time they arrived at the Opal Empress, however, the cymotes had killed all the passengers of the Opal Empress, including Drake. As they made their way through the ship, Aphra and Starros discovered that the dead bodies of the passengers, though they were unsure of what had caused all the deaths. The two headed to a cabin to find Drake, and Aphra heard noises that came from the vents, that unbeknownst to her came from the cymotes, Aphra asked Starros if she had also heard them, and when she questioned what Aphra had heard, the noises stopped. Eventually they discovered Drake's corpse and what his big opportunity was, an invitation to a Crimson Dawn auction where they planned to sell off the smuggler Han Solo. As Starros and Aphra discussed the auction, they were fired at by the bounty hunter Durge, who had arrived to claim a bounty on Drake.
As Aphra and Starros spoke with Durge, the cymotes came out of the vents and attached themselves to Durge, although he was able to get them off him, and the trio made their way into a room. Aphra realized what the creatures were and informed Starros of what they were up against. After Aphra mentioned that they were supposed to be extinct, Durge claimed he could fix that. Starros asked if the cymotes had any weaknesses and Aphra revealed their sensitivity to atmospheric changes. With this, Starros suggested sending them out of an air lock and they made their way towards one. Durge lured the cymotes into the air lock, though he was also jettisoned him into space alongside the cymotes by Aphra. Because of the rapid decompression, the cymotes exploded when they were exposed to space.