Kueller was a Force-sensitive Human male who was originally known as Dolph. At some point before 17 ABY, he was a student at Luke Skywalker's Jedi Praxeum on Yavin 4. Early in his training, Dolph's homeworld of Almania experienced a purge by the Je'har, the ruling government, who sought to crush all who resisted them, including Dolph's parents. The pain and anguish resulting from their deaths caused him to leave the academy and turn to the dark side of the Force. He changed his name to Kueller and began a resistance movement to wipe out the Je'har. With the power of the dark side at his command, he succeeded in his goal by utterly destroying the Je'har and their sympathizers and also attracted another one of Skywalker's failed students, Brakiss, as an apprentice. In the process, he wiped out the populace of one of Almania's moons, Pydyr.

However, even with the Je'har defeated, Kueller sought revenge against Skywalker and the New Republic for not aiding the people of Almania when they had come under attack. He placed Brakiss in charge of a droid manufacturing facility on Telti, and used it to produce a large number of explosive-rigged droids for sale to the New Republic, including many that were used in its fleet of X-wing starfighters. When Kueller activated some of his droids, a series of explosions ripped through the Senate Hall on Coruscant, injuring Chief of State Leia Organa Solo and sowing discord through the New Republic as part of his plan. In response, Skywalker pursued his former pupil to Almania, but Kueller sabotaged the Jedi Master's X-wing. After a crash landing, the injured Skywalker was easily captured, but managed to escape. Meanwhile, Organa Solo took a New Republic fleet with her under the command of General Wedge Antilles to confront Kueller. The Dark Jedi ordered his subordinates to engage the New Republic fleet while he dealt with Skywalker. When Kueller caught up with Skywalker on the surface of Almania, he bested the weakened Jedi Master and threatened to kill his newly-arrived sister, Organa Solo. However, Han Solo and Mara Jade arrived soon thereafter, along with a ysalamir; the Force-repelling bubble effect of the ysalamir and the arrival of Skywalker's friends threatened Kueller's advantage. Outraged, he prepared to activate another round of detonator-equipped droids, but his bombs were deactivated by C-3PO and R2-D2 who were on Telti,and he was fatally shot by Leia Organa Solo, ending his plans for a new rebellion.

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