Doctor Chen Bax was a scientist formerly affiliated with the Office of Naval Intelligence.
Chen Bax never wanted anything to do with the military, dreaming of ways he could improve humanity's daily life if peace prevailed. During the Human-Covenant War he served under ONI as a civilian, working on several projects which helped humanity's survival. During his work in ONI he met Doctor Luciana Rutan in a chance encounter, whom meeting lead Chen to make a choice which would give him the peaceful life he wanted.
Chen then supported ONI with distinction until he grew disillusioned, believing that the organization no longer represented humanity's best interest. He stole classified technology, but before ONI could apprehend him and recover what he'd taken, Chen was believed to have been killed in action during the Fall of Reach.
Life and death on Sephune III
In late 2553 ONI received a distress call from the planet Sephune III which indicated that Chen had survived, along with others from the UNSC Promise of Dawn. The doctor held considerable knowledge, and was considered by ONI to be a liability, and ordered Spartan Linda-058 to remove him from the picture before that knowledge fell into the wrong hands.
Chen proved himself to be a capable leader, keeping the survivors alive in hostile territory for around a year, on a planet that was dominated by members of Jul 'Mdama's Covenant. He manipulated his followers into believing that the UNSC had abandoned them and that the Covenant were blocking their comms, when it was, in fact, him. He claimed to be building a new nav unit for the new build ship which would get them to safety, when in reality Chen's goal on Sephune III was to retrieve the AI Gabriela. This was a mission which he kept from all but a few of his followers. In hiding the truth, he denied them the ability to make an informed choice about staying on the planet. He trekked to crash site of the Promise of Dawn with the Spartan, knowing that she would be able to access the AI stored there, intending to take it for himself. During the journey, he tried to convince Linda to abandon the UNSC, though she refused, and Chen attempted to kill her while he gained control of the AI. Even using turrets, and an assault rifle, he was no match for the Spartan-II.
Overpowered and shot in the leg by Linda, Chen gave his followers the chance to escape by giving them the location of the nav unit for the newly-built ship, setting off the Promise of Dawn's self-destruct to cause an avalanche. The avalanche took out a large portion of the Covenant ground forces, allowing the humans to escape, at the cost of his own life.
List of Appearances