Sidonie Garen was a female Human Jedi Master of the Jedi Order. During the time of the Cold War, on Alderaan, Sidonie fell into a terrible illness under the Sith Lord Vivicar, which caused her to go insane. And the timing couldn't be worse, as Alderaan was hosting a secret peace summit between all the noble houses, as Sidonie attempted to provoke continued war. The Jedi Council sent the Jedi Consular, the future Barsen'thor, to find her, and was able to cure her, freeing the Jedi Master from her insanity.
During the Great Galactic War, Sidonie went on a mission to Malachor III along with Eriz Vossan, Yuon Par, Cin Tykan, Duras Fain, and Parkanas Tark. However, during their mission on the planet, Garen and the Jedi uncovered some terrible evil and were nearly affected by the spirit of Terrak Morrhage, a long-dead Sith Lord of the Old Sith Empire. Developing a plan to escape from the dark planet, the Jedi when Vossan fell behind until Parkanas saved him, but became trapped in the process and was left behind by the other Jedi. Garen felt responsible for the loss of Tark.
In 3643 BBY, Master Garen was stationed on Alderaan, a former planet that was part of the Republic until it fell into a civil war after Queen Silara Panteer and Prince Gaul Panteer were killed, and a corrupt noble named Bouris Ulgo, a descendent of Trask Ulgo, usurped the throne. She had been working hard to organize a peace treaty between the noble houses of Alderaan, in an attempt to stop the war. However, before she could continue her assignment, she fell to Lord Vivicar's plague and raised the Jedi Council's suspicions by dropping out of contact for some time.
As the peace summit was due to occur, Alderaan was visited by Yuon's Padawan, a gift Jedi Consular, who was seeking all the Jedi Masters afflicted by the plague. When called via holo, Sidonie was quick to dismiss the Consular as a mere Padawan and refused to give her location. Somehow learning or anticipating that the Consular would seek out House Teral, the only house lacking a delegate for the summit, and that Teral would endorse the Consular by cementing an alliance between their house and House Organa, Sidonie hired House Rist to kidnap Lew Organa before he could meet with the Terals. However, Lord Teral informed the Consular, who went to rescue Lew. Afterwards, they discovered Sidonie's holofrequency on the Rist base's computers and get the Jedi Master on the holo. Discovered, Sidonie quickly excused herself.
As the summit began in the Sendoth Ruins, Sidonie ordered the guards to bar anyone else from entering. During the summit, the plague-affected Jedi Master had already proceeded to bring war on Alderaan due to her madness. Clouded by the plague which made her aggressive, she believed that the only future for Alderaan was war, so she brought incriminating evidence on each of the Houses to the summit, reminding them of old grudges, and spurring escalation of the conflict. When the Consular managed to calm the delegates down, the enraged Garen engaged the Jedi, unleashing her Force powers. The Consular bested her in combat and was able to use the shielding technique to save the insane Master. Regaining her senses, Sidonie noted that the Consular seemed weak from shielding her. Apologizing for her actions, Sidonie left handling the summit to the Consular and reported back to the Jedi Council.
The Consular choose to shield her for light side points or kill her for dark side points.