|Role||Son of an ISA Ambassador, the key to Mandor Savic's virus|
|Affiliation||ISA, Helghast, Phantom Talon Corp|
Justus Harkin es el hijo del embajador de Vekta, Sepp Harkin, y una mujer Helghast, Valeria Harkin. Por lo tanto, es mitad humano y mitad Helghast.
Durante la invasión de Helghan, Justus y su familia se encontraban bajo arresto domiciliario, que la inmunidad de su padre de cualquier tipo de daño ha sido anulada por la invasión. Debido a que su padre es amigo cercano del Almirante Grey, que tiene el sombrero de la inteligencia que lo salvó de la muerte durante la invasión de Vekta, ella tiene la intención de devolver el favor enviando mercenarios para rescatarlos y ponerlos en buenas manos.
During the assault, he and his family are hold up in one of the rooms, where the family's bodyguard, Boris holds off the attackers. Tragically, his father and mother are shot and killed. Moments later, the mercenary, Arran Danner, arrives and Justus is escorted by Danner and Boris to the docks, where they intend to escape by boat. After fighting through helghast soldiers, Justus and Danner succeed in escaping to the docks. However, Boris dies in the effort. Before leaving, Justus laments that he can never come back nor will he ever see his parents and Boris again. He is eventually taken under the care of Admiral Grey, who keeps him close at all times, knowing his value as he had the bioweapon trigger inside of his bloodstream, apparently unknown to Justus himself. Eventually, Danner comes to take the virus and rescues Justus from the research facility. Once they get off the facility Blackjack then wipes their tracks so Justus can be a normal kid again.
- He is the second half human/half Helghast, the first being Gregor Hakha.
- He is the first child to ever appear in a Killzone series game.
- He is voiced by Spike White.