Diortem is a strategic city located in Southern Vekta. Prior to the Helghast invasion, the city was treasured by Vektans. Here, the ISA researched technology for use in the war. The city was the location of an ISA bioweapon program.
During the initial invasion on Southern Vekta, Diortem was one of the first locations to be captured by the Helghast. At the request of General Armin Metrac, Helghast Colonel Vyktor Kratek was tasked with invading the city. After successfully taking the city, Kratek had several senior ISA members held hostage. Among these hostages was the ISA Admiral Alex Grey, who headed biological weapons research in Diortem.
Following news of Grey's capture, the ISA requested the aid of the Phantom Talon Corp, an elite group of mercenaries to rescue Grey. PTC operatives Arran Danner and Damian Ivanov rescued Admiral Grey in the Halls of Justice from being executed by Kratek. Even with the admiral safe, the war in Diortem wasn't over yet. A downed Helghast cruiser lay stranded, depriving the entire city of power in an attempt to repair itself and leave the planet with stolen ISA weapons technology. Danner and Ivanov were tasked in infiltrating the ship, where they managed to download the Helghast's transmission codes and sabotaged the ship. Unfortunately, a failsafe left Ivanov quarantined, where he died trapped inside the ship's explosion.