Gregor Hakha is a young half Helghast who works for the Colonial Intelligence Service in the ISA as a secret agent. Prior to his defection, he was a trusted aide and friend to General Joseph Lente, the mastermind of the Helghast invasion of Vekta. At one point, Hakha even served as Chief of Staff to Lente.
Holding the rank of Colonel, Hakha defected to the ISA shortly before the invasion of Vekta, opposing the authoritarian nature of Scolar Visari. He was immediately marked for assassination by the Helghan invaders of Vekta. Shortly after his ISA bodyguard was struck down, he was rescued from certain death by Captain Jan Templar, Sergeant Rico and Shadow Marshal Luger and worked with them in defeating General Lente.
When the mortally wounded Lente seeks to spite him by telling Hakha that Lente had ordered his brother killed on Helghan, Hakha promptly executes him with a shotgun shell. As for Hakha's other relatives, it is known that his mother is Helghast and his father Human. He is an expert in Helghast weaponry and technology, as possesses strong technical and espionage skills. He also heals faster than an ordinary human.
He is wise and very intelligent, judging by his vocabulary, and sometimes quotes philosophers and poets alike. He often clashes with Rico because of his Helghan heritage. Although his Killzone confrontation with General Adams is not canon, it is the most dramatic and well versed of all 4 possible endings.
While he does not make an appearance in following games, it is believed that he retired his military commission and aided the Vektan Council in preparing for their counterattack against Helghan, even suggesting that Luger be dispatched to eliminate Scolar Visari and end his threat once and for all.
- "You try to compare us?... You made a choice, General, based on your own goals and morals. As did I. We may both seem traitors by our outside appearance, but that is where our common ground ends."
-his reply to General Adams when being compared to himself.
- "Given time, even a monkey could write Shakespeare." - in response to the squad's agreement with Rico's idea of a head-on attack against a Helghast code 3-3 firebase.
- "Well, those of us with even remotely developed minds rise above the frailities of the flesh, and cope with it." - in response to Rico's anti-Helghast attitudes following his rescue.
- "Right, well, a special forces captain falls in love. He promises her the world, but she has other plans. Nine months later, they meet again, except now the brave captain's sweetheart is a cold assassin. Trained to kill. Trained to think, not feel. Act, not reflect. Oh, she's almost perfect. Though I doubt Captain Templar feels otherwise." - explaining to Rico the nature of Templar and Luger's relationship.
- Gregor Hakha is voiced by Sean Pertwee, who also voices Colonel Mael Radec in Killzone 2. Sean Pertwee is the only voice actor in the series to play Helghast characters against and in support of Scolar Visari.
- The StA-52 assault rifle is Hakha's favoured weapon and shows above-average accuracy with it.
- Hakha is the first known "half-breed" in the series, with both Human and Helghast blood. The second being Justus Harkin, a young boy, son of the Vektan embassador, appearing in Killzone Mercenary.
- He is the first playable Helghast in the campaign mode of the Killzone series. Echo of Killzone: Shadow Fall only has one level.
- He can pilot an Overlord Dropship.