Fey was born in 1910. Her mother died in childbirth, and she was raised solely by her father. She was recruited to the British Intelligence forces in 1933, and quickly gained a legendary reputation in the service. (COMIC: The Clockwise War)
Fey first encountered the Eighth Doctor in an unrecorded adventure involving psychic weasels in Russell Square. On that occasion the Doctor gave her a Stattenheim Summoner that could contact his TARDIS. (COMIC: Tooth and Claw) In 1937, the Threshold kidnapped Fey and put a mind control device in her head to spy on the Doctor. (COMIC: Wormwood)
In 1939, Fey called on the Doctor and his companion Izzy to help her investigate the sinister Varney; in the process of defeating Varney, the Doctor began to die. (COMIC: Tooth and Claw) Using the knowledge given to her by the Threshold, (COMIC: Wormwood) Fey piloted the TARDIS to Gallifrey, where the Doctor's body was cured and his mind placed into the Matrix to heal. (COMIC: The Final Chapter) There, after the Doctor foiled a plot of Overseer Luther, he regenerated into a new incarnation. (COMIC: The Final Chapter)
However, this was a ruse. The Doctor had realised Fey was under external control when she had piloted the TARDIS even though the TARDIS manual was in Gallifreyan script, which she couldn't have understood. Just before the Doctor prepared to sacrifice himself, Shayde offered to take his place and fake a regeneration. This would allow them to bring a newly regenerated and weaker Doctor to them. Both disguised with personal chameleon circuits, Shayde would hold their attention while the Doctor sabotaged the Threshold's operations.
In Wormwood, a Wild West town on an alien moon run by the Threshold, the Doctor's plans came to fruition. The Threshold removed their implant from Fey, gloating she had been an unwitting spy for them. Preparing for the final confrontation, Shayde and the Doctor revealed themselves to the Threshold. However, Shayde had to contend with the Pariah, an immensely powerful prototype version of himself. Shayde could not defeat the Pariah on his own and she crushed his skull. Comforting the dying Shayde, Fey merged with him and together they killed the Pariah and eliminated the Threshold. The shared being was dubbed Feyde by the Doctor, although each of them retained consciousness. Feyde decided to leave and deal with what had just happened to them. (COMIC: Wormwood)
Fey returned to 1939, where she continued to work for the British government. Fey spent two years fighting the Nazis with Shayde, though she felt some frustration because Shayde would not allow her to use their powers to kill Adolf Hitler, as this would have changed history. Over the course of their union, Fey and Shayde began to develop a close love/hate relationship, sharing secrets, but often vigourously disputing the use of their power to influence history. Fey resented Shayde's unwavering loyalty to Rassilon and his lack of individuality. These traits implied she was in love with Shayde, but could not admit this to herself or her partner. (COMIC: Me and My Shadow) In 1941, she received a sub-ether summons from the Doctor — Izzy had been kidnapped and the Doctor needed Shayde's abilities to track her on the planet Oblivion. They recovered Izzy. After Izzy was restored to her own body after having exchanged it with Destrii's, Fey encouraged her (Izzy) to embrace her true sexuality and gave her a passionate kiss. Feyde returned to World War II. (COMIC: Oblivion)
During the Time War
Fey was reunited with the Doctor in his next incarnation, where she was recruited by the young War Doctor to fight in the Last Great Time War. He plucked her from World War II and had her travel with him. To the rest of the world, she was believed to have been killed in action as a British agent in 1944. Fey earned many titles throughout the War, such as "The Silent Shadow", "The Soldier of the Unknown", and "The Dark Reward". The Daleks called her "Haruk Za", which translated as "The Death of Light".
Fighting alongside the Sisterhood of Karn, the Doctor and Fey fought the Morlontoa of the Seventh Sky. Fey ordered Time Lord Captain Dolios to get the childlike inhabitants of the planet, the Loshann, to a TARDIS. The Sisterhood were then struck by a stream of pure chaos, leading the Loshann to be hit by the spores of the Morlontoa. They were quickly inverted, turned into monsters and attacked. To save themselves and other Loshann on the planet, the Doctor ordered Fey to shoot each of the Loshann. After she did so, the Doctor's machine to save the planet failed, and the planet would fall anyway, rendering Fey's killing of the Loshann meaningless.
While the planet was saturated by the spores, the Doctor ordered his allies back to his TARDIS, but Fey saw a child in the wreckage and saved him, wasting time she didn't have. Fey and the child were touched by the spores and melted away, as the Doctor, unable to save them, watched from his TARDIS. (COMIC: The Clockwise War)
After the Time War
Despite appearances, Fey did not die, as she teleported herself away to the Dreamspace at the last possible second. She also believed the child to have been rescued as well, not knowing that he was dead all along. She convinced herself that she had nurtured the child to maturity, with him taking up the name of the Absence. In the real world, a badly injured and delirious Fey materialised in the college dormitory of her future nephew, Alexander Truscott. After he learned of the Time Lords' meddling in history, he began to warp her mind and turn her against them as she healed. She separated Shayde's mind from hers under the belief it was Truscott's work, while Truscott used her powers to create the Clockwise Men. Eventually, Fey recovered and began to work with Truscott. In doing so, she sabotaged the Time Lords' regeneration code and recovered a map of the entire space/time vortex in a plan to wipe out the Time Lords, all the while believing to be working under the Absence. (COMIC: The Clockwise War)
With his dying breath, Sythorr warned the Doctor that “the unknown soldier” was returning. (COMIC: The Soul Garden) Fey was responsible for drawing the Stikini, a race of creatures from the Dreamspace, to the medicine woman Totika, which the Twelfth Doctor fought. (COMIC: The Parliament of Fear) After the Doctor defeated the Phantom Piper, another creature from the Dreamspace later revealed to be under Fey's control, she appeared before the Doctor to warn him that the Absence was coming, and that he should assemble his forces, before taking off. (COMIC: The Phantom Piper)
Later on, Fey worked on a plan to capture time travellers so she could find the Doctor. This led Count Jodafra to a decaying time machine, the Rangiroa, stranding him in the middle of an entropy bubble in space that Fey had placed there. The Doctor was eventually drawn to the ship, with everyone else believing that he was behind Fey's actions. During an attack by the Clockwise Men in the entropy bubble, Fey reappeared to throw Jodafra into the Clockwise Men against the Doctor's wishes, killing him. She later attempted to shoot the Doctor and Bill Potts on Cornucopia, where she was intercepted by Annabel Lake. The air-truck she was riding on eventually crashed into the ground and exploded, but Fey was left unharmed.
The Doctor eventually used a copy of Fey's favourite childhood book, Peter Pan, to meet her in the Dreamspace, where she revealed her intentions to him. As Truscott's plans later came to fruition, Shayde began to reconstitute himself around Fey, with her announcing to the creatures of the Dreamspace to prepare for war. With the Doctor and his allies entering her area of the Dreamspace, Fey briefly fought Annabel again before being faced down by the Doctor. After Bill got her to listen, he explained to her how she was behind all the events and the Absence never existed. With her illusion broken, the sphere shattered, returning everyone to reality.
With Fey unconscious in the aftermath of the battle, Shayde finally reappeared, dying. To prevent Fey's death along with him, he transferred his remaining essence to her, while wiping her memories of everything after bonding with him so she could be at peace. With Shayde gone, the Doctor secretly placed her at Wonderland in London, although he never said goodbye to her, under the hopes of one day seeing her again. (COMIC: The Clockwise War)
As a merged entity, Fey was able to use Shayde's powers, including the ability to travel through time and space unaided, phase through solid objects and fire self-generated "psychic bullets". (COMIC: Me and My Shadow, Oblivion) Even with her and Shayde's minds split, Fey was still able to harness some powers, including teleportation and intangibility. She seemingly lost these abilities after Shayde freed her of his presence again. (COMIC: The Clockwise War)