Born on Vekta into a military family, she strove to prove herself to her father and brothers. She graduated top of the class in the Navy Academy. She became a decorated officer, distinguishing herself in several campaigns including Delta Pavonis, Omicron Eridani, and also negotiated an end to the Arcturus Insurrection.
She was appointed First Lieutenant of the Cruiser Solar Wind, and was eventually promoted to Admiral in 2349. She attempted a diplomatic approach towards the Helghast sending Sepp Harkin as an ambassador, wanting to avoid a Second Extrasolar War. Negotiations failed, which would eventually lead to the invasion of Vekta. She then headed the defense of Diortem that was at first more effective than the ISA's defense of Northern Vekta.
During the Helghast invasion of Vekta, heavy fighting took place around a strategically vital city, Diortem. Admiral Grey, who was responsible for defending the city, was taken hostage by Vyktor Kratek during the fighting at that location. At the request of the ISA, Anders Benoit launched an extraction mission at the Halls of Justice in an effort to save Grey.
Two mercenaries named Arran Danner and Damian Ivanov carried out the mission, escorting the injured Alex Grey from the battlefield. Two years later, Grey requested Phantom Talon Corp for a demolitions mission on Helghan. The mission, which revolved around the destruction of Helghast arc cannons, was a success.
During the invasion on Helghan, Grey was tasked with saving the ISA ambassador Sepp Harkin, as well as his family, from the Helghast. Grey once again requested Anders's mercenary Arran Danner for the mission. The mission was somewhat of a failure, with Danner only managing to save the ambassadors son Justus.
Grey then learned that a Helghast scientist named Mandor Savic had also managed to escape the embassy. Grey agreed to save Savic from Helghast forces, and in return receive valuable intel on Kratek. Soon after, the ISA was once again under threat from the Helghast arc cannons.
Grey soon learned that the arc cannons power was being supplied via a Helghast refinery. After taking out the refinery, Danner is left for dead by a paranoid Grey. Kratek decides to rescue Danner, as he still required his services.
Interrogations with Savic revealed that a bioweapon capable of destroying an entire planet was being held in a vault inside a secret research facility. Soon after, Grey learns that Danner is the only living person who knows the codes required to detonate the weapon. After locating the secret facility, Grey reaches the vault only to find that Danner has already retrieved the weapon. Danner then kills Grey and leaves the rigged facility.
In the testimony gained from her from interrogation, it is revealed she edited Savic' testimony to make it appear as though the Helghast launched the attack. It also suggests that this operation was carried out on her authority alone, given that she drafted the testimony to exempt the ISA of blame. She also wrote that she once believed in the possibility of peace, but that the events on Vekta changed her view, concluding that despite the price of countless millions dying, she believed it would be worth paying to end a conflict that would embroil a generation.
- She is voiced by Lucy Newman-Williams.
- As of the release of Killzone: Mercenary, Admiral Grey is the only female enemy character fought in the series, as well as the only female character the player can choose to kill.
- Grey has two possible death scenes; she can be downed in combat, then executed with a special quick-time event, or Danner can skip the fight with her entirely and lock her in the virus containment chamber; she will bang on the door and curse Danner until the bombs in the chamber detonate and incinerate her.
- Her last word's should Danner interrogate her are: "So Kratek - wins -?"
- Grey is the only ISA antagonist that did not betray the ISA.
- Grey appears to be in command of ground forces during the invasion of Helghan, this is strange as an Admiral would be in control of Navy vessels and not ground forces. She has the unusual discrepency in common with Admiral Orlock. This is even noted by some of the ISA Marines under Grey's command, who question why she has authority over them, and Grey's superiors in the ISA do note that she is outside her jurisdiction by commanding ground troops.