Triumvir Ilia Volyova was an implant-free Ultranaut who served aboard the lighthugger Nostalgia for Infinity and was responsible for monitoring and investigating the Cache Weapons. It was during her search for a means to control the hell-class weapons that she recruited -- or more accurately, abducted -- Ana Khouri (who was planted in the role by the Mademoiselle), in 2546.
Ilia maintained a long friendship with her captain, John Brannigan, and was the only one to visit him regularly during his necessary confinement in very deep reefersleep, used to slow down the onset of Melding Plague in his body. She later disengaged the reefersleep and warmed him up fully, allowing his body to merge with the Nostalgia for Infinity as the only way to save it from an attack.
Decades later, in a plot hatched with Khouri, Volyova helped organize the evacuation of Resurgam, the first human-colonised planet to be destroyed by the Inhibitors. She prevented the suicide of Captain Brannigan, by then indistinguishable from the ship. By doing so she exposed herself to hard vacuum, the damage proving nearly fatal, but preserving the ship and thus the last chance of survival for the inhabitants of Resurgam.
She later died on a suicide mission attacking the Inhibitors around Resurgam in an attempt to slow them down, giving the Nostalgia for Infinity the best possible chance of escape.
Her actions -- while heroic -- had no measurable effect on the Inhibitors or their solar weapon, and all cache weapons that she took were presumably destroyed.