Vialco, a Human male and Dark Side Adept, loyally served the Galactic Empire. As an apprentice under High Inquisitor Antinnis Tremayne, he gained notoriety for hunting down Jedi fugitives. He also became known for invading their dreams with his own terrifying visions. Stationed with the garrison on Nysza III, where the Empire was constructing a new communications bunker, Vialco's service took an unexpected turn. The Harrier Infiltration Team, operatives of the Alliance to Restore the Republic, disrupted the construction. In defense, Vialco killed agent Arecelis Acosta and clashed with the aspiring Jedi, Fable Astin.
Vialco triumphed over Astin, who escaped with Deke Holman, the only other surviving member of the infiltration team. The Dark Jedi pursued Astin, using the Force to torment her with horrifying premonitions of her demise, where he was a terrifying figure. He eventually found her on Trulalis, where she was training under the former Inquisitor Lord Adalric Cessius Brandl. During their duel, Vialco quickly realized Brandl had significantly improved her skills. The battle concluded with Astin defeating Vialco, and showing no mercy, she swiftly beheaded him.
During the Imperial Period, Vialco, a Human male, was a servant of the Galactic Empire. As a Dark Jedi in training under High Inquisitor Antinnis Tremayne, a former Jedi Padawan, he believed he would eventually succeed his master. He was known to figures like the rogue Inquisitor Lord Adalric Cessius Brandl, due to his infamous telepathic abilities. Vialco exploited the vulnerable, planting illusions and visions in their minds, a practice Brandl considered cowardly. Throughout his service to Tremayne, Vialco relentlessly pursued and killed fugitive Jedi Knights, managing to avoid punishment from his master and Emperor Palpatine, despite his difficulties serving under non-Force-sensitive officers.
In 0 ABY, Vialco was assigned to the Imperial garrison on Nysza III, where the Empire was building a communications bunker. Subsequently, agents of the Alliance to Restore the Republic, known as the Harrier Infiltration Team, attacked the site. The team, consisting of Socorran Deke Holman, Coynite/Human hybrid Arecelis Acosta, and aspiring Jedi Fable Astin, infiltrated the site with the goal of destroying it. Vialco confronted Acosta, toying with him before ultimately killing the hybrid. He then engaged Astin in a lightsaber duel in one of the construction corridors. With a feint, Vialco sent Astin flying across the garrison. As the Dark Jedi mocked her, she succumbed to the dark side of the Force, lashing out in anger. Astin and Holman then succeeded in destroying the construction site and escaping Nysza III.
Vialco survived, and using the Force, reached out to Astin, invading her dreams. His goal was to fully turn Astin to the dark side. In his first attempt, her mind was transported back to her mission, before encountering Vialco, when she and Acosta were trapped by stormtroopers. In the dream, Vialco replaced Acosta and attacked Astin, tempting her with the dark side's power. She awoke, knowing that Vialco was coming for her and wanted her to embrace the dark side. Vialco reached out a second time while she was flying an X-wing starfighter through hyperspace. He conjured a vision of Acosta's body and sent it crashing through the fighter's cockpit windshield. Astin felt as though the air was being sucked from her lungs as her cockpit opened to space, and Vialco reappeared, laughing mockingly. The vision ended, leaving Astin disturbed.
Vialco learned that Astin was training on Trulalis under Inquisitor Brandl. He traveled to Trulalis in a shuttle, landing near the town of Kovit. He proceeded to The Barrows, a graveyard, to wait for Astin. When the Jedi arrived, Vialco was surprised by her newfound maturity and that Brandl, known for his vindictiveness, had taken her in. He sensed her thoughts, finding her determined to avoid more nightmares. Announcing his intention to kill her, Vialco attacked, surprised when she successfully parried his strikes.
They exchanged words, and Vialco intensified his attack, his anger growing. He conjured an illusion of Acosta, but Astin was not deceived. She slashed Vialco's shoulder, sending him crashing against the tomb of Brandl's wife. Astin taunted him, threatening to do to him what he had done to Acosta. Enraged, Vialco realized he couldn't convert Astin and summoned Force lightning, hurling it at her. Three bolts struck her, knocking her down. As he gloated, she rose, and he continued his barrage. This time, Astin deflected the bolts with her lightsaber, anticipating his attacks.
She advanced, knocking him into a depression. The lightning turned against Vialco, burning him severely. He reached for his fallen weapon but fumbled, pushing it further away. Astin approached, weapon raised to kill. The Dark Jedi groveled, and the Jedi hesitated. Lord Brandl urged her to kill Vialco to prevent further dream invasions. After a brief hesitation, Astin swiftly beheaded the Dark Jedi. Brandl had created an illusion of Vialco rising with his weapon, prompting Astin's action. Brandl intended to turn Astin to the dark side and present her to Emperor Palpatine on Byss. However, the young Jedi fled with Brandl's son, Jaalib, and her compatriot Holman.
Vialco was considered unattractive, with a gaunt face, angular features, white hair, and large eyebrows. He was vindictive when haunting Fable Astin, reminding her of her failure to save Arecelis Acosta. He used the incident to try to sway Astin to the dark side, arguing that her passion could have saved Acosta. Vialco believed anger controlled actions and power stemmed from fear. He called the dark side "ultimate ecstasy" and believed it was the true form of power. When threatened, he became cowardly, groveling before Astin after she defeated him. Ambitious, he sought to advance within the Empire and succeed Antinnis Tremayne as High Inquisitor. His success as a Jedi hunter occurred despite his inability to work with non-Force sensitive officers and his ego.
Vialco was skilled in lightsaber combat, outmatching Fable Astin in their first encounter. His telepathic powers allowed him to prey on the vulnerable and invade Astin's mind from afar, affecting her dreams. He could insert himself into her thoughts and taunt her as she slept. In one vision, he made it seem as though the air was being sucked from Astin's lungs into the vacuum of space, even though she was safe. He could also do this in combat. The Dark Jedi could summon powerful bursts of Force lightning, but when knocked off his feet, he lost control, and the lightning turned on him, burning through his clothing and flesh. Vialco could also use the Force to absorb energy, control pain, resist stun attacks, and detect the Force in others.
Vialco was created by Patricia A. Jackson in her 1995 short story, "Uhl Eharl Khoehng," published in Star Wars Adventure Journal 8. The character was later mentioned in Jackson's canceled work Emanations of Darkness.