Background
When the sun rises, it is beautiful. Before its light reaches the horizon, however, there is darkness all around.
Karna's conception occurred when two Pantoran politicians began an illicit affair with one another. At the time where the pregnancy was discovered by the two, Karna's mother, Ailise Chuchi, decided she would keep the child, and raise it without knowledge of who his true father was. The father, Naida Ishii, asked only one thing of her. To name the child Karna.
Happy but ignorant, Karna's older half-sister Riyo doted on him as a babe, but a Jedi Seeker arrived for the child before he was three years old. Karna was a Force-sensitive. Given leave to take the child, Karna began his journey to Coruscant. There, his training began, and the sun began to rise.
Karna proved a studious, open-minded, and cool-headed youngling, afflicted with only one true fault. Fear in the face of danger held him in its tight vise, warping and bowing him even during training exercises. To help him overcome his fear, he was assigned to Master Cin Drallig, a patient, focused, and incredibly skilled Jedi duelist.
Over the course of the next several years, though Karna could never overcome the trembling in his fingers, he grew willful enough to ignite his lightsaber and face whatever stood across from him. Under the guidance of Master Drallig, Karna grew into a capable duelist, and one well-regarded and friendly with many of his peers.
On the onset of the Clone Wars, with Cin Drallig the Battlemaster and head of security at the Coruscant Jedi Temple, Karna was instead paired up with a close friend and her master, Arycelle Dania and Master Andoras, respectively. Over the course of the Clone Wars, the relationship between Karna and Arycelle grew into a powerful bond. However, the death of Master Andoras at the hands of Darth Maul late into the Clone Wars saw the two returned to Coruscant and stationed within the Jedi Temple.
There, Arycelle stewed with the prospect of vengeance against the former Sith. A darkness crept over her, sinking beneath the surface, and she eventually left Coruscant, seeking Maul out on Mandalore. Having followed her aboard the ship she'd commandeered, the two argued, and eventually Arycelle ignited her lightsaber, demanding Karna remove himself from her path. Trembling with the usual fright and now sadness at how his friend's grief had twisted her, Karna met her blade with his. Within their ship, Karna overcame his wrathful friend, but in the process the ship's controls were heavily damaged, leaving them alone and adrift in space.
In order to save their lives, Karna reached out to the Force, to the bond he still considered unbroken between them. There, a Force Bond was forged. Entering a meditative state while attuned to Arycelle's unconscious mind, Karna was able to keep them both sustained with life for nearly a month, before finally a ship caught their distress beacon and located their drifting ship.
In it, Karna saw old friends and masters, survivors, he learned, of a terrible betrayal that had taken place shortly after they had left Coruscant. The Jedi Temple on Coruscant now lie in ruins. The clones and the Republic had turned upon them, branding them traitors and to be killed on sight.
Eventually, Arycelle returned to consciousness. Taken to a hidden refuge containing the surviving Jedi, she was resuscitated and then informed of what Karna had learned days earlier. Here, on Ashas Ree, an old Jedi temple had been built upon the ruins of an ancient Sith one, and here these survivors met to discuss the future. It was clear that secrecy must be their creed, but Arycelle and others argued that inactivity would prove a death knell to their Order. Instead, they must make moves to bring down the rising Empire, and see that the Order was restored.
In this dispute, several members walked away, departing Ashas Ree. Karna wished to be among them, but the bond he'd weaved with Arycelle drew him to stay. At the time, he'd hoped to curtail her dark need for vengeance, as she'd seemed somewhat returned to herself since awakening. Over the next several years, he would eventually realize that he'd been a fool, blind and ignorant to how changed she truly was.
The missions they undertook gradually grew more and more dubious in their purpose. When once they'd focused on freeing other Jedi, now the call went out to slay Inquisitors and Moffs. Karna brought this change before the group, who had begun to call themselves the Last Flame, and found an insidious change had taken place within them all. Throughout the years, hard as they were, suffering losses and losing friends, Arycelle's way of thinking had slowly given strength to the others. It was the destruction of their foes that now pumped through the veins of these former Jedi. The resurrection of the Jedi Order - the true Order - could not be brought about from those Karna saw standing before him.
Karna made to leave, but his once-allies blocked his path. Arycelle appeared before him, speaking these words.
"Maul, the Emperor, his inquisitors and pet Vader - they will all pay. Any who claim the name of Sith will meet their end before the justice we will mete out upon them. Pick your side Karna. With us, or against us."
Trembling as he always did, Karna forced down his fear and made his choice.
A broken lightsaber in his hand, too many wounds to count, Karna fled Ashas Ree, barely able to stand. The only reason he'd survived was because of the Force Bond he shared with Arycelle. For if he died, so would she. In trying to capture him, to chain him up beneath the temple, he'd managed his escape.
Wounded, feverish, and with no certainty of where to flee to, Karna input the coordinates to a marshy planet he barely remembered. Arriving back to Pantora, he looked for, and eventually found, the home he'd laughed within beside his sister. There, he met his mother again, who cared enough still of her long departed son to take him into her home, to nurse him back to health.
His sister, Senator Riyo Chuchi, soon arrived, throwing her arms around a brother she'd seen only in passing during the Clone Wars - the Jedi having ensured that no familial bonds be rekindled, as was their way. From there, he learned much of what had transpired in the Senate since the Emperor's rise to power, and, more shockingly, there they learned the truth of his birth.
At the age of 26, Karna met his father for the first time. Infirm and retired from politics officially, Karna found Naida Ishii a man still toiling. Helping Ailise from behind the scenes, the two led those Pantorans seeking self-sufficiency in a system plagued by marauders, slavers, and pirates. The Empire had all but left them to flounder on their own, as Pantora remained one of the few planets where its senator questioned the changes occurring within the Empire. Finding a purpose he could believe in, Karna promised his aid.
Within a year, he learned of an imperial prison on a planet only a sector away from Pantora, where several political prisoners from Pantora had been incarcerated. He also learned that the Empire had made deals with roving marauders to capture those Pantorans, and then would pay them to bring them to Alzoc III. Fear and dread took him, but once more he forced it down. It was a simple task to venture out and allow himself to be captured by a band of pirates in the system, and soon he was on his way to Alzoc III.
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Note: Since his arrival on Pantora, he has made sure to limit his connection to the Force, as using more than a few drops will surely send tremors through the bond he possesses with Arycelle - for he feels them whenever she wields the Force, which has been often and wracked with rage since he fled Ashas Ree.
Motivation
Faith: The Sun will Rise. Karna believes in the tenant that any night must end, and that hope in the sunrise will abate the horrors writhing in the dark. One must not lose hope or let the darkness mangle them before the sun's light shines over them once more.