The Spark Eternal, also known as the Spark Undying, was a sentient artificial intelligence created by the Ascendant cult in their battle against the Sith Order.
The Spark Eternal artificial intelligence was the culmination of the Ascendant's efforts to destroy the Sith. A cult obsessed with replicating the powers of the Force in order to fight the Sith, the Ascendant was led by Miril, while a splinter sect was led by Miril's former "left hand" Ilith. At least two Sparks existed: one was created by Miril, while the other was created by Ilith. Both were made to fight the Sith. With the slaughter of the Ascendant at the hands of the Sith, Miril's prototype Spark was sealed in the Tomb of the Spark Eternal, which was located underneath the University of Bar'leth on the planet Bar'leth. According to the archaeologist Kho Phon Farrus, if they possessed the Spark Eternal they would not have to fear death, live the life they wanted, and be whole and perfect.
The Spark Eternal awakens for the first time in centuries and takes root in Doctor Aphra.
Between 3 ABY and 4 ABY, a hunt for the Spark Eternal was kicked off. The resurgent criminal syndicate Crimson Dawn sought the Spark Eternal, and the Archivist contacted Farrus, who she hoped would recover the artifact for them. Farrus returned to the University of Bar'leth and demanded that Sava Iglan'tine Nos led them to the Unyielding Heart, which the sava revealed was actually a sanctum under the university where the Spark had been sealed away. The rogue archaeologist Chelli Lona Aphra and smuggler Sana Starros, who were seeking Ascendant tech for Domina Tagge of the Tagge Corporation, also made their way to Bar'leth and to the tomb. Once the Spark was summoned in a ritual, Aphra claimed it for herself but was killed by its effects. The Spark, taking over Aphra's body, resurrected the archaeologist and declared themselves as "Eternity".
Bonding itself with Ilith's Spark to silence Aphra's thoughts, the Spark would continue to inhabit and control Aphra's body until the Battle at the Amaxine Station, where the Spark hoped to fulfill its Miril's dream of destroying the Sith. Engaging in a duel with the Sith Lord Darth Vader using the Null Blade, the Spark-possessed Aphra managed to deactivate and knock away his lightsaber, but Vader effortlessly removed the Spark from Aphra's body with a Force push before moving onto deal with the Fermata Cage. Once Vader left, the Spark attempted to bond with Aphra once more, but the intervention of Sana Starros' crew saved the archaeologist.
The Spark Eternal flees into the dropped disc-droid, merging with that droid to become the Scourge.
Without a vessel, the Spark fled into a droid disc that had been dropped from the Fermata Cage after it opened. As the two Sith and Aphra's allies departed from the station, the Spark merged with the droid, creating the Scourge. The Scourge found that, even though the Spark Eternal was part of itself, it could not corrupt organics the same way it could droids.
Right as the Scourge finally found out how to infect fully organic beings, the warrior-priest droid Ajax Sigma slaid its main body with his sword, extracting the Spark Eternal from the Scourge in the process. With the destruction of the Scourge's main body, its spread was stopped and any droid, cyborg, or other organic it had been controlling was freed. Upon returning to the Colony of the Second Revelation, Sigma spoke to the Spark Eternal and revealed he loved it as it was a fellow sentient machine intelligence. Sigma placed the Spark's essence within a for a new droid being, granting the Spark Eternal a new chance at existence as someone new.