Oenone Zero was born on the Aleutian Islands about two years before the events of Mortal Engines, making her approximately nineteen or twenty when she is introduced, four years older than Wren Natsworthy.
She started playing with Stalker parts when she was a young girl growing up in Aleutia, and she soon was called to repair the Stalkers of the Green Storm when the experts were unsure of what to do. She enlisted into the Green Storm later, rising to a high rank in the Resurrection Corps.
Oenone Zero was first seen on the Black Island, digging up the Stalker Shrike, who has been killed by Tom Natsworthy eighteen years previously. After a few months of working and restoring him, Oenone presented him to the Green Storm's leader, the Stalker Fang, who accepted him and appointed him as her bodyguard. Shrike later overheard Oenone in a chapel in Tienjing, asking God for help to assassinate the Stalker Fang, he decided to inform the Stalker Fang but due to the settings that Oenone had fixed into him, he could not utter a single word of her plan.
During the attack on Cloud 9, Oenone questioned Wren and Theo about the Tin Book of Anchorage. Upon learning that the Tin Book possibly contained the codes for the Old Tech weapon ODIN, she left to activate the secret code she had installed inside Shrike's mind, as he was her assassination weapon against the Stalker Fang all along. The Stalker Fang knocked Oenone unconscious in the resulting duel. She woke up to see the pavilion burning, and she was rescued by General Jiang Xiang Naga, who congratulated her for killing the Stalker Fang, as he did not approve of the Stalker Fang's disregard for the lives of his soldiers. He then took the raiding party and prisoners, along with Oenone, back to Tienjing.
A Darkling Plain
Oenone married General Naga, using her influence to encourage peace talks between traction cities, static settlements and the Green Storm. These efforts were not received well by some members of the Green Storm, resulting in the formation of some splinter groups intent on her assassination. After travelling to Zagwa, she treated Theo Ngoni after he hijacked and crashed an airship belonging to one such group.
In an effort to fool her enemies, Oenone was secretly transported to Shan Guo aboard the Nzimu by Theo, along with Captain Rasputra and her servant, Rohini. Rohini, in fact extremist agent Cynthia Twite, killed Rasputra and nearly strangled Oenone. Cynthia left after Theo interrupted her assassination attempt, setting off an explosion aboard the airship.
However, both Theo and Oenone survived and were captured as slaves aboard Cutler's Gulp. Grandma Gravy, recognising her as Naga's wife, sold her to Napster Varley. She saved Hester Natsworthy, who later saved Oenone. As Hester and Zero make their way back, Kriegsmarschall von Kobold found them and helped them.
Zero was informed of Naga’s demise, and was appointed leader of the Green Storm, which she turns into a new Anti-Traction League. She made a treaty with von Kobold to cease fighting forever, with many traction cities becoming static.
Dr. Zero is shown to have been very close to her family. Her father was a Green Storm soldier who was killed in the attack on Rogues' Roost in Predator's Gold. Her mother was an airship pilot who was killed sometime between Predator's Gold and Infernal Devices. Her brother Eno, with whom she was best friends and whom she loved dearly, died around the time that she first became an officer in the Resurrection Corps. She was forced to turn him into a Stalker, and after she did so, she vowed to end the war between the Traktionstadtsgesellschaft and the Green Storm by assassinating the Stalker Fang.
Oenone Zero is mistrustful of most of the religions in the world, but she is attracted to a small Christian chapel in Tienjing, which allows her to be cynical about Christianity, saying "What on earth was the use of a god who went around getting nailed to things?" She is similarly cynical about other religions, though she returns to the chapel to pray and to read a T.S. Eliot poem written on the wall. She feels drawn to the poem, and she uses one of its lines as the activation code that would trigger Shrike's impulse to assassinate the Stalker Fang.
By A Darkling Plain, Oenone has become a Christian, though she has little understanding of theology. She finds comfort in the Christian God, whose presence she felt when she thought she was dying on Cloud 9 after attempting to assassinate the Stalker Fang with Shrike. The ideas of forgiveness and peace play an important role in her decisions and world view.