Syl, a female Human who exhibited sensitivity to the Force, was a student under the tutelage of Satele Shan during the era of the third Galactic War. Syl, along with Shan and the other students, fell victim to Tenebrae's curse. Kira Carsen and Scourge confined them within a large vessel. Ultimately, the Commander of the Eternal Alliance freed them and vanquished Tenebrae permanently. Despite initial beliefs that she had died, Syl miraculously pulled through.
Following the war against Zakuul, Syl became one of the many Force-sensitive individuals to join a new group of students that Jedi Master Satele Shan began training at a clandestine Jedi academy situated on Coruscant.
When Satele Shan was unknowingly infected by the affliction of the deceased Emperor Tenebrae, Syl and the other followers likewise became infected. They were plunged into a state of nightmarish slumber, gradually coalescing into a collective consciousness. Scourge, a Sith Lord, and Kira Carsen, a Jedi Knight, maintained their quarantine aboard Carsen's ship, which traversed an erratic course through the uncharted areas of the Outer Rim Territories.
After the Commander of the Eternal Alliance successfully released the majority of the followers from the curse, permanently ending Tenebrae's existence, Syl was presumed to have perished, much like her fellow student Trad. However, against all odds, she survived the infection.
Following the Tenebrae incident, Syl, now back on Coruscant, observed the meeting between Master Satele Shan and the former Jedi Aryn Leneer. Later, Syl interrupted their conversation, informing Satele that Master Sal-Deron wished to speak with her at her convenience. She barely acknowledged Aryn before departing the room. Satele and Aryn briefly discussed Syl's behavior after her departure, prior to meeting with Sal-Deron.