From Star Trek: Theurgy Wiki
Junior Lieutenant Hi'Jak used to be Assistant Chief Science Officer at Starbase 84. After the Battle of Starbase 84, Hi'Jak was forced to defect to the USS Theurgy because of circumstance. Hi'Jak then aided in the opposition against the parasites that compromised Starfleet Command in the end of the 24th century. Not long after his defection, he was abducted by the Savi, and underwent Correction upon the Versant. Afterwards, he was no longer a Klingon and Human hybrid, since the Savi removed all traces of Klingon genes.
Hi'Jak was born a half breed son on Qo’Nos, his father was a Klingon, and his mother a Human who was more (Klingon) in spirit. Hi'Jak was, however, dwarfed and eclipsed by siblings from his father's previous marriage. Since he was never given his father's House, and was more of an outcast from a young age, he had a dream to form his own house.
To establish a House was simple, anyone who was a Captain in the Klingon Defence Force could - in time - get their own house, and generals often sat on the Council. Jack would only need to climb the ranks, and so from a young age he set forward on that goal and enrolled himself into the academy of the first city to try and become a warrior.
The only problem with this was that Hi'Jak was an awful warrior. He was far better with numbers and technology. However, his regular classes did not last long. He was fifteen when he was pulled out of his bed, and dragged into a room with several other young half breeds. He was addressed by High Chancellor Gowron. Hi'Jak was told that they had no interest in using half breeds as warriors, that they were a shame to their families, and held little purpose within the empire, but if they forswore honor and glory seeking, then they would have a greater purpose in Imperial Intelligence.
Hi'Jak’s education was furthered from that point on, training in the sciences helped to further the goal of infiltrating the true enemy of the Empire: the Federation. It was around the age of eighteen that he was swept up in an affair with a young, but abusive Klingon female, whom he married, and never divorced. She beat him to near death several times, and seemed to despise Jack taking pleasure in his suffering.
He ran from Qo’Nos when he got his assignment to join the Federation, working the Federation's Science Division. Once Hi'Jak got to the Federation, started to slack off. He did graduate with a Masters in Animal Psychology, a study of animal behavior and evolution on various worlds, including co-habitual evolution, and animal husbandry across the worlds of the Federation. In the end, he got a bachelor's degree in Temporal Mechanics, a study of advanced Temporal Theory, case studies and lots of complicated physics and math.
After his completion of the Academy years, he was going for a posting as far away from Klingon space as he could, yet ended up quite close to the KNZ, and had to occasionally send boring letters to Imperial Intelligence to maintain his position and cover. At the same time, he was struggling with the crew of Starbase 84 - the location he was assigned. His superior officer - Simon Walt - was a xenophobic, sexist human, who annoyed and grated on Hi'Jak, causing all of his own work to slow in progress . When Hi'Jak finally had enough and tried to transfer, his requests were denied.
During the Battle of 84, Hi'Jak acted as an investigator in a case where a Romulan’s head exploded below the base's Subspace Acquisition Grid. During the investigation, he helped to uncover a hidden message with some trickery he had picked up in Imperial Intelligence. He attempted to hand over that secret communication to the captain of 84, Ian Hawthorne, who instead gave the order for Hi'Jak and Ensign Six’s arrest.
Hi'Jak had returned to his lab, to oversee scans of findings by Sera vers Aldnoah, taking a puzzle box that the computer core of 84 could not recognize. Then, Jack was attacked by base Security, and while he tried to spare lives during the fight, the Simon Walt was killed by Sera vers Aldnoah. In the end, Hi'Jak escaped thanks to Sera and the Sabine, joining up with the Theurgy crew.
The biggest problem facing Jack was not his discontent for authority or even his halfbreed status it was in fact much simpler than that. Hi'Jak had a failure with commitment. When running was no longer an option he would face a problem and even achieved better than expected results, but his intellect could be a waste without rigid deadlines. Were it a simple failure to manage time then this problem would have been less rooted, and Hi'Jak would have become one of the science divisions most promising members. However, his problem could be seen in all of his activities and not just his work.
In his relationships, Hi'jak was likely to run. Pinning down one date or night with the man was easy enough, keeping him - however - was much more difficult. His commitment to people lacked fervor, and he was known to get cold feet in certain situations. He was awkward for many reasons, but this was among the top, as he could easily shrink away from it and avoid the person he was in a relationship with. He was especially uncomfortable with Klingon women.*
*Counselors note: While Jack was born on Qo'noS he does not seem to hold traditions or honor in high regard. His discomfort with Klingon Women seem stem from his first sexual encounter in a Klingon mating ritual that ended with him receiving two broken ribs, carpet burns, and a pulled calf muscle.
There is little doubt that Hi'Jak is intelligent, his minor in Temporal Mechanics and his analytical mindset are all assets to the science division. However current opportunities for command positions have been denied to him due to his lack of overall commitment. While he does have the mind and skills for Starfleet duties, he lacks the overall spirit for leadership, and requires a push to get results.
Hi'Jak was born a hybrid, Human and Klingon, and his genetics were a staple in his physiology, everything from the curves of his forehead ridges less pronounced than a regular Klingons. He also had three lungs, and improved physical endurance, strength etc.
Not long after his defection, he was abducted by the Savi, and underwent Correction upon the Versant. Afterwards, he was no longer a Klingon and Human hybrid, since the Savi removed all traces of Klingon genes. At this time, Hi'Jak had also lost his right eye and right arm, surgically removed above the elbow, but he could possibly get cybernetic prosthetics to replace those later in the year 2381.
Image: Potentially Hi'Jak later in the year 2381, as a Human with cybernetic prostetics.