"The Jedi Order betrayed me..."

At the wake of the bombing of the Jedi Temple, Ahsoka Tano was unfortunately at the wrong place at the wrong time, for she was framed for causing the bombing and banished into exile from both the Jedi Order and Coruscant. Angry and betrayed, Ahsoka slowly yet gradually fell to the Dark Side; not as a full-on Sith, but as a Dark Jedi. As a shadow of her former self, she hunts down surviving Jedi across the galaxy to make them feel her resentment and betrayal.

(Image Source: boppeto, Reddit)

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In the wake of the bombing of the Jedi Temple, Bariss Offee was never discovered to be the true culprit behind the heinous act and brought to justice. Despite Ahsoka Tano's fervent pleas of innocence, along with the arguments of Anakin Skywalker, the evidence planted against her was already damning. The Jedi Council, shaken by the attack on their temple and pressured by the Galactic Senate to make a response, had no choice but to expel Ahsoka from their order and hand her over to the Republic to stand trial, even though they believe in her innocence.

Normally, as a result of the Clone Wars being at its height and much of the courts and law enforcement being replaced with martial law and the suspension of habeas corpus, such a crime would be punishable via the death penalty. However, the Jedi Order was able to convince the court to have Ahsoka be given a lighter penalty, so she was sentenced into exile from Coruscant, forced to leave behind the only life she had ever known.

As she journeyed through the vast expanse of the galaxy, alone and adrift, Her heart was heavy with anger and resentment, emotions that gnawed at her soul and threatened to consume her; the dark side of the Force, with its honeyed yet venomous silver tonguing, began to whisper to her, offering solace and power in exchange for her pain.

(Despite it all, her exile was what saved her from the massacre of the Jedi Order during Order 66 at 19 BBY.)

Ahsoka, desperate for a sense of belonging and purpose, found herself increasingly drawn to the dark side's seductive promises. She began to dabble in its power, justifying her actions as a means of survival in a galaxy that had turned its back on her. In the midst of this, she was found by Bariss Offee, now an Inquisitor for the Empire. She had Ahsoka fall further into her dark impulses due to how the two of them agreed on how the Jedi Order had fallen from grace.

Ahsoka, now a Dark Jedi, fully embraced her dark impulses. She ventures around the galaxy with a black cloak and two Sith-ified Darksabers, hunting down any surviving Jedi she encounters to make them feel her anger and resentment.