Vialco was a Dark Jedi in the service of the Galactic Empire. He served with the garrison on Nysza III, where the Imperials were constructing a new communications bunker. At some stage, the construction was harried by the arrival of the Harrier Infiltration Team, agents of the Alliance to Restore the Republic. Vialco defended the construction site, and did battle with one of the team members, an aspirant Jedi named Fable Astin. Vialco overcame the Jedi and slew another Alliance agent, Arecelis Acosta, but the bunker was destroyed. Astin and the only other remaining member of the Harrier Infiltration Team, Deke Holman, were able to escape.
The Dark Jedi hunted Astin, and through the Forceplagued her dreams with nightmarish visions of her doom, in which he would appear to frighten her. He eventually tracked her to Trulalis, where she had been training under the auspices of former InquisitorLordAdalric Cessius Brandl. Vialco dueled the young Jedi, and soon discovered that her skills had been greatly enhanced by Brandl. The duel came to an end when Vialco was outfenced by Astin, and when he was at her mercy, the Jedi unceremoniously decapitated him.
Vialco survived, however, and through the Force, reached out to Astin, pervading her dreams. It was his hope that he would be able to turn Astin fully to the dark side. In his first effort, her mind was cast back to her mission, before she had encountered Vialco and was trapped by stormtroopers, along with Acosta. In the dream, Vialco took Acosta's place and attacked Astin, luring her with the power of the dark side. The Jedi woke from her dream, but Vialco had been able to leave no doubt in her mind that he was coming for her, and that he meant for her to embrace the dark side. Vialco reached out to Astin a second time, when she was flying an X-wing starfighter through hyperspace. He conjured a vision of Acosta's body and sent it flying into the fighter'scockpit, through the windshield. To the horrified Astin, it felt as though the air was being sucked from her lungs as her cockpit was now open to space, and Vialco appeared to her again, mockingly laughing at her. Vialco's vision then ceased, leaving Astin perturbed.[1]
Vialco duels Fable Astin on the plains of Trulalis.
It came to Vialco's attention that Astin was in training on Trulalis, under the instruction of none other than Inquisitor Brandl. Journeying to Trulalis in a shuttle, he landed near the township of Kovit. Disembarking, the Dark Jedi made his way to The Barrows, a graveyard, and there he waited for Astin. The Jedi soon approached, and Vialco was surprised at her new found maturity. In particular, he was surprised that the infamously vindictive Brandl had even taken her in. He reached out and sensed Astin's thoughts—she was assuring herself that she would experience no more bad dreams. Announcing his intent to kill her, Vialco drew his weapon and attacked, but was once again surprised when she successfully parried his strikes, without sacrificing any ground.[1]
The two bandied words, and Vialco doubled his attack, his anger rising. Conjuring another illusion in her mind, he brought back the memory of Acosta, but Astin was not to be fooled. She sliced at Vialco's shoulder and sent him hurtling against the tomb of Brandl's wife. Astin taunted Vialco, threatening to do likewise to him as he had done to Acosta. Enraged, Vialco realized that he could not convert Astin to the dark side, and summoned Force lightning, hurling it at his opponent. He struck her with three bolts, bringing her to the ground. As he gloated, she rose to her feet once more, and he continued his barrage. This time, however, Astin was able to deflect the bolts with her lightsaber, anticipating each of Vialco's attacks.[1]
She gradually made her way toward him and knocked the Dark Jedi into a depression. The barrage of lightning began to turn against Vialco, burning him severely. He reached out for his fallen weapon, but fumbled, only causing the weapon to move further from him. Astin approached, weapon held aloft with the intent to kill. The Dark Jedi writhed, adopting a grovelling manner, and the Jedi hesitated. Lord Brandl approached, and insisted that Astin kill Vialco, lest he invade her dreams once more. Although Astin hesitated briefly, she lashed out and decapitated the Dark Jedi swiftly. Brandl had inserted an illusion of his own into her mind, of Vialco rising up with his weapon drawn, inspiring Astin's decisive action. It had been Brandl's intent to turn Astin to the dark side himself and present her to EmperorPalpatine on Byss. The young Jedi, however, fled with the assitance of Brandl's son, Jaalib, and her compatriot Holman.[1]
Vialco was considered an unattractive man, with an angular face, gaunt cheeks and unusually large eyebrows. When haunting Fable Astin, Vialco became overly vindictive, reminding her of her failure to prevent Arecelis Acosta from being killed. He used the incident in an attempt to sway Astin to the dark side, stating that had she given in to her passion, she would have been able to save Acosta. It was Vialco's belief that anger provided control over actions, power could stem from fear itself. He referred to the dark side as the "ultimate ecstasy," and held the belief that it was the true form of power. When truly threatened, however, Vialco would resort to cowardly behavior, grovelling before Astin when she had bested him in combat.[1]
Vialco was a skilled combatant with a lightsaber, able to deftly outmach Fable Astin during their first encounter. His telepathic powers allowed him to prey on the weak minded, and invade Astin's mind from great distances, affecting her very dreams. He could even insert himself into her thoughts, and goad her as she slept. In a later conjured vision, Vialco was able to make it seem as though the air was being sucked from Astin's lungs and into the vacuum of space, although in reality she was perfectly safe. Vialco was also able to do this in the heat of combat. The Dark Jedi was also able to summon powerful bursts of Force lightning. When he was knocked off his feet, he could no longer control his power, and the lightning turned on him, burning through his apparel and flesh.[1]