Codename: REGAN is as mysterious as any ONI spook. She never reveals personal details, she knows all the details of those she operates with. Her age, name and home are all unknown. For a ONI spook she has a high level of knowledge, knowing about and participating in Operation: HYPODERMIC, Operation: TREBUCHET, the SPARTAN-IIs and SPARTAN-IIIs, the secret of Red-0112.
Her first major operation was TRECBUCHET, having infiltrated a United Rebel Front faction on Hectate, she posed as a young intelligence officer while feeding information to the UNSC forces ahead of their strikes and aiding the escape of SPARTAN-013 from the facility. She was not seen again till the Battle of Morigan III where she was taken prisoner by the Covenant forces who marauded through the facility she operated in. She and two her fellows were tortured for information but she held out until the Spartans of Black Team rescued her. After sometime of operating, she was caught out again by the Covenant, being caught in CASTLE Base during the battle of Reach. With her transport off world destroyed, she decided to make use of an old ONI base to try and evacuate with her ONI staff but found the Chiroptera-class Stealth Vessel there was decommision. By chance, she happened upon SPARTAN-013 and SPARTAN-039 and used his prodigous techincal skill to fix it before escaping. Once in orbit she and the others were picked up by one of her old comrades, Captain Zachary Drogen. After that she reassigned herself and Sierra-013 to his NavSpecWar group and operated on SpecOp missions of high importance, providing a commanding force on the ground during operations.