Osia was a male Human who was Force-sensitive. He dedicated his service to the Believers, a Sith cult, during the closing years of the era of the Galactic Republic. Around 21 BBY, Osia participated as a member of a Believers team. Their mission was to travel to a secret base located on the moon of Tilnes. This base belonged to the Metatheran Cartel, a trading organization. The team's purpose was to analyze the effects of a virus that the cult had unleashed within the facility. Upon their arrival at the base, the cultists were ambushed by Ko Bas, a deranged Caarite mutant. This attack resulted in the death of four members of the group, leaving only Osia and Aris, another Believer, as survivors. Approximately three hours later, Osia and Aris launched a surprise attack on a group of freelance agents who were present at the base, but they were ultimately defeated.
Osia, a male Human with Force-sensitivity, gave his allegiance to the Believers, a Sith cult, during the final years of the Galactic Republic. In approximately 21 BBY, Osia was part of a six-member Believers group. They were instructed to meet at a bar in the floating city of Tolea Biqua on the planet of Genarius to get ready for a coming assignment. Two weeks earlier, the cult had orchestrated the introduction of a new experimental virus that was fatal to the Caarite species. This occurred at a secret base belonging to the Metatheran Cartel, a trading enterprise, situated on the moon of Tilnes. Osia and his companions were assigned to assess the virus's impact on the base's inhabitants. Osia was only informed of the mission's crucial aspects, remaining unaware of how the team would communicate their findings or the Believers' broader strategy to weaken the Metatheran Cartel using the virus.
The cultists journeyed to Tilnes on a starship and proceeded to the Cartel facility, located within a network of tunnels deep beneath the lunar surface. Shortly after they got to the base, an electromagnetic pulse originating from Tilnes's core struck the facility. This activated an emergency security protocol that sealed the doors, trapping Osia and his comrades inside. The Believers soon discovered that the virus had not killed all of the base's residents. Ko Bas, a Caarite, had been transformed by the contagion into a horrifying mutant creature and attacked Osia and the other cultists. Bas killed four of the slower members of their party, while Osia and the Believer Aris evaded his clutches and fled into the depths of the Cartel facility in search of a safe place to hide.
Osia and Aris sought refuge in a hidden security office and encountered two other mutant Caarites, U and G. By using the Force to influence their minds and by speaking to the mutants in their native Caarite language, the two Believers subdued the mutants and brought them under their control. Osia and Aris subsequently tried to bypass the base's security system to allow them to leave the Cartel facility, but their attempts were unsuccessful.
Three hours after Osia's arrived at the Cartel base, the heroes of Cularin–a renowned group of freelance agents–entered the facility while investigating a distress signal. Their arrival took the Believers by surprise and Osia and Aris watched on unseen as the operatives fought and overcame Ko Bas and recovered an active specimen of the viral contagion. The Believer pair resolved to prevent the operatives from leaving the base so as to ensure that knowledge of the pathogen remained a closely guarded secret.
Accompanied by U and G, Osia and Aris confronted the heroes of Cularin at the entrance to the base as the agents attempted to leave. They revealed themselves to the operatives and Osia issued an ultimatum that the agents either surrender their virus sample and leave unharmed or be killed. The heroes of Cularin refused to hand over the viral specimen and Osia and Aris attacked them while urging the two mutant Caarites to slay the agents. However, the Believers were defeated, allowing the heroes of Cularin to take the virus sample away for analysis.
Osia, a dedicated follower of the Believers' ideology, believed that the cult's enemies would face death and destruction. As was typical among the Believers, he had a tattoo on his right shoulder depicting the spire of the Sith fortress on the planet Almas.
Osia possessed skill in various Force abilities, which included sensing, mind manipulation, enhancing his physical attributes and healing himself and others. Besides Basic, he had the ability to speak the Caarite language.
During his mission on Tilnes, Osia carried a blaster pistol and a stun baton. He also wore a blast helmet and blast vest, along with a respirator to protect himself from the anti-Caarite virus.
Morrie Mullins created Osia, who appeared in Caaried Away, a roleplaying adventure from March 2003. This adventure was part of RPGA's Living Force campaign and served as the opening chapter of the Metatheran Caution trilogy. In the adventure, players take on the roles of the heroes of Cularin. If the players agree to Osia's demand to hand over the anti-Caarite virus specimen, Osia and Aris allow the agents to leave without interference. After the operatives have left, two Believers then make their way through a different set of tunnels to the agents up to the surface of Tilnes and head to the cultists' starship.
If the players refuse to surrender the virus, Osia and Aris attack them and it is possible for Osia to be incapacitated or killed. If he is captured, he attempts to commit suicide by strangling himself with the Force. If the player characters succeed at preventing him from killing himself it is possible for them to persuade him to provide them information about the Believers' mission. If Osia and Aris defeat the freelance agents, they collect the viral sample and depart the base accompanied by the mutant Caarites U and G, leaving the player characters alive as the cultists had no orders to kill any non-Caarites.