As a male Human who sided with the Sith Empire during the Cold War, Vector Hyllus existed. On a diplomatic mission to Alderaan, he transformed into a Killik Joiner, yet he held onto enough of his original self to stay a dedicated Imperial agent. Furthermore, he was known to be associated with Cipher Nine.
Vector Hyllus belonged to the second generation of Imperials; his mother was from the Jurio system and married Captain Adronik Hyllus after the Empire took control of Jurio. From a young age, Vector showed a strong interest in joining the Imperial Diplomatic Service and possessed the necessary qualities. He excelled academically during his training and, shortly after graduating, his request was granted when he was assigned to a vessel focused on exploration and first contact. During his time with the Diplomatic Corps, Vector visited the industrial facilities on Fest, which were filled with hazardous areas that caused illness among many workers. Due to the need for diplomatic personnel, he was reassigned to Alderaan to work with the House of Thul. He performed admirably until he encountered the Killik species and underwent the subsequent transformation into a "Joiner". According to Doctor Eckard Lokin, Project Protean orchestrated Vector's meeting with the Killiks to study the Joining process. As a Joiner, he held the position of Dawn Herald for the Oroboro Nest, serving as a warrior and emissary who faced the unknown. In his role as Herald, Vector was more than just a typical Joiner, as he maintained a sense of his individual identity.
Cipher Nine was dispatched to identify and neutralize the source after the Eagle's terrorist network's funding was traced back to Alderaan. The Imperial Agent encountered Hyllus and gained access to House Cortess despite the initially hostile actions of Baroness Chay Cortess. After securing an audience with the Baron, the Cipher Agent acquired a lead indicating that Denri Ayl, a respected Alderaanian mediator, was connected to the terrorists after reviewing the library records of House Alde.
During this period, it was discovered that Baroness Cortess herself was also assisting the terrorists. The Imperial attempted to confront Cortess, but she ordered her guards to prevent the agent from entering. Consequently, Hyllus brought in Killik reinforcements, which resulted in damage to the Cortess shield generator in the Glarus Valley. After fighting their way into House Cortess, the agent exposed the Baroness's betrayal to her husband, Peyar Cortess. House Cortess was not implicated as a whole; however, appropriate responses and precautions had been taken. Vector Hyllus was designated as an asset under Cipher Nine's control, and a permanent transfer from the Diplomatic Service was approved.
After Doctor Lokin realized Vector's link to Project Protean, Lokin and Vector both attacked Project Protean's headquarters. They both questioned the woman in charge and obtained answers. Lokin learned why they wanted him dead and how his research was used to advance Project Protean, while Vector had his files erased and stopped further Killik experiments. After this, Lokin became the new leader of Project Protean. Even though Vector said he would never trust Doctor Lokin, he was happy that they were on the same side.
As Vector continued his travels with Cipher Nine, he searched the Imperial Citadel's database for any signs of other Killik Nests that had migrated away from Alderaan centuries ago. After experiencing dreamlike memories of the Great Migration of the lost Killik Nests, Vector requested leave to embark on a pilgrimage to retrace the steps of their lost Killik relatives. Upon his return, he reported that he was unable to locate any of the lost Killiks and could only conclude that they had eventually split into thousands of nests, each following its own path. Shortly thereafter, he was contacted by another Dawn Herald: Daizanna of the Iesei Nest. Both Killik Nests celebrated their reunion and invited the Agent to join in their festivities.
Having discovered the resources and advantages of the vast Killik civilizations throughout the galaxy, Vector proposed a Killik-Imperial Alliance to the Imperial Diplomatic Service. Unfortunately, the Diplomatic Service disregarded his report. An old colleague, Falner Oeth, contacted Vector and proposed an alliance. In exchange for Falner's promise of future support for his Killik alliance proposal, Vector and his Killiks would use their resources to perform clandestine tasks for him and expand his influence. After completing Oeth's favors, Oeth received a promotion and, despite expressing his repulsion towards the Killiks, he fulfilled his part of the agreement. Oeth arranged a summit between the Killik representatives and key members of the Diplomatic Service. Following some negotiations and instances of trade, relations between the Imperials and Killiks improved.
In the meantime, Vector underwent certain changes. Vector received a message from his former love Anora who pleaded with him to return to Dromund Kaas so they could reverse his "joining". Vector had contemplated her message and had come to the conclusion that he was content with his new life as a Joiner. Vector had also gone through the Chrysalis of Tranquility: a ritual used to strengthen the Dawn Herald and enhances his link to the universe.
After consulting with various ambassadors of the Sith Empire, the Diplomatic Service finally agreed to an official treaty with the Killiks. At the summit to formalize the treaty, the proceedings were sabotaged by a bomb that resulted in Daizanna's death. Falnar Oeth claimed responsibility for the bomb and delivered a public address denouncing the Killik-Imperial Alliance. Nevertheless, the Imperials proceeded to legitimize the Killik-Imperial treaty, and the Imperial-Killik alliance was officially established. The Killik Nests offered Vector the position of Dawn Herald of all Killik Nests but refused the position as he felt his priority was being the Agent's companion and covert assault operative.
During the Eternal Empire's Conquest, the Cipher disappeared. Vector felt as the starship grew cold in his friend's absence. During the conflict, the Sith Empire used the Killik as cannon fodder, resulting in the wasteful deaths of many, as a result, Vector declared that the surviving Oroboro Killik no longer recognized the treaty with the Sith Empire.
Vector Hyllus consistently expressed his admiration for the achievements of the Empire, while also demonstrating his desire to expand Imperial influence through diplomatic means. His views were likely influenced by the Imperial reconstruction of his home planet and are consistent with those of a member of the Diplomatic Service. Hyllus was known for being obedient, intelligent, charismatic, and effective. It was unlikely that he would have advanced further in the diplomatic or military ranks.
Vector Hyllus serves as one of the companions that players can choose in the Imperial Agent class in Star Wars: The Old Republic, and he is a potential romance option for female characters. Ifan Meredith provides his voice.