Abersyn symbiotes were a species which feed on the brain stem of sentient species. They had to be fed into a plasma furnace in order to keep them in a quiescent state, though a regular exposure to a plasma vent has been proven to have the same effect on them. They were known for being responsible for the death of many historical empires, therefore, having a specimen was banned by Imperial decree.
During her time as a doctoral student in the University of Bar'leth, Aphra was studying and exploring the planet of Boothi XII looking for an incredible discovery. After finding nothing on Boothi XII, Toob-Nix, Aphra's doctoral supervisor, showed her a full nest of Abersyn symbiotes in his personal chamber, telling her why he hated her so much and that he would never give her his approval to get the doctorate. As revenge, Aphra stole the whole nest with the help of Sana Starros and made it appear as if she had finally found the Abersyn symbiotes on Boothi XII. As a part of the Imperial protocol, the symbiotes were disintegrated right away.
On Ktath'atn, the Queen of the planet kept several Abersyn symbiotes that she used to control her collection. She attempted to use them on Aphra and Luke Skywalker as a feigned "dessert", but proved unsuccessful when Aphra realized the trap and escaped with the Padawan. Aphra later found a large colony of the symboites and 0-0-0 directly implanted one in Black Krrsantan so he would go berserk and attack the Queen's followers.
- Doctor Aphra 1: Aphra, Part I (First appearance) (Appears in flashback(s))
- Doctor Aphra 2: Aphra, Part II (Mentioned only)
- Doctor Aphra 5: Aphra, Part V (Mentioned only)
- Star Wars 31: The Screaming Citadel, Part II
- Doctor Aphra 7: The Screaming Citadel, Part III
- Star Wars 32: The Screaming Citadel, Part IV
- Doctor Aphra 8: The Screaming Citadel, Part V
- Star Wars 33: Rebels in the Wild (Indirectly mentioned only; in the opening crawl)
- Doctor Aphra 10: The Enormous Profit, Part II (Indirect mention only)