Aife is a Light Fae of Clan Finarvin but doesn't abide by their rules. She is the daughter of Trick, born when he was The Blood King. Her mother was Isabeau, who was betrayed and killed during the The Great War between the Light and Dark Fae. While posing as Saskia, Afie claimed to be Dark Fae.
Long ago, the two Fae clans, Light and Dark, were at war with each other and fought to the point where they were almost driven to extinction. The Blood King could see that the Fae were only hurting themselves with their warring and used his powers as a Blood Sage to change destiny, forcing a truce between the two sides, and writing the Blood Laws under which they have since continued to exist. His powers, however, always come with a consequence: Aife was unhappy with this unstable agreement and created a small band of rebels against the truce.
To avenge her mother's death she assassinated a Dark Fae Elder. She went to The Blood King for protection, but instead he handed her over to the Dark for execution. Rather than being put to death, she was held prisoner for centuries by a Dark King, tortured, and raped. Aife was unable to overcome her captor as he had a Koushang, which bound his chi to his body, nullifying Aife's succubus powers.
While Aife was imprisoned she became pregnant by the powerful Dark King, and remained captive before she was able to escape after giving birth to Bo. (Her escape to freedom was due to Trick's intervention – he had filled books full of blood in attempts to help her, though previously being unsuccessful.) Her midwife was a fellow rebel, Lou Ann, a member of the Dark Fae. After killing the nanny that was taking care of the infant Bo, she declared that Bo would never belong to "him" and took her. Lou Ann then managed to escape into the woods with Bo in her arms.
While Aife was hunted and apprehended (another downside to Trick using his blood powers), Lou Ann was helped by Will, a Will-o'-the-wisp. She found humans that could care for Bo in secret, and left the infant with them. As revealed by Cassie, the Dark Fae Oracle, Aife had once again escaped from prison, but this time for good, and she was searching for Bo.
Aife finally found Bo and had been watching her for a long time. She approached her at a singles bar while Bo was investigating a case, introducing herself as "Saskia." (The Mourning After)
The bar was Aife's feeding territory and she confronted Bo and Kenzi with the excuse that Bo was trespassing on it. When she was told about Bo's detective business, Aife was intrigued. She tags along (wanting to spend time closer to her daughter), explaining that she wanted to know who was killing on her territory, and interested in teaching Bo about being a succubus, and how to use her powers, when the investigation was over.
The two do some investigating and interrogating of the singles night organized by Bertram, Bo manages to get a list of people in his program from, but overall they don't really get anywhere with it. Allison, the girl who was murdered had a sister, who was the one who hired Bo in the first place, and she was murdered that night in the same style as her sister. Bo and "Saskia" go to Collette's house only for "Saskia" to see the stylized killing for the first time and demand that they leave. She explains that an Albaster, natural enemy of the succubus that creates sexual shame rather than pleasure, is behind the murders, and that they need to figure out who it is.
They first go after Carter, who had sex with Allison the night before her suicide, and "Saskia" interrogates him this time. She manages to make him reveal that he didn't kill Allison before almost killing him, but as Bo is having a fit, "Saskia" gives Carter some energy of her own and brings him back to life. Bo is ecstatic and asks for "Saskia" to teach her, but she only says that she will after they're done with the case.
Bo goes home without "Saskia", only to find Bertram waiting for her, he reveals himself as the Albaster before attacking Bo. She manages to hold him off with her own power for a while but he is stronger and prevails in the end, making Bo feel depression like never before. During this time, "Saskia" had called Bo and when she didn't answer she got worried, so she rushed over and saved Bo from Bertram. Bertram is then tied up and the two succubi use their powers to make him abandon his previous beliefs about sex being wrong, making people sluts. Bertram begs for more but Bo decides he's had enough and she goes to call Dyson to pick Bertram up. "Saskia" has a different idea though as she drains Bertram of his energy, leaving him to die. Bo comes back and asks "Saskia" to revive him but she refuses. She says that since he attacked Bo the Dark won't care that he's dead, unless they find out "Saskia" killed him. "Saskia" then leaves as Bo argues about how it was wrong.
Aife returns as Saskia again to fix things with Bo, seeing Dyson for the first time as well, Bo refuses a night on the town as she and Dyson are working on a case together. Saskia says that being with one person isn't what succubi do as it's against their nature before leaving.
Dyson, now ready to tell Bo who she is, was waiting for her to show up at his office where he is confronted by "Saskia". She attacks him and reveals that she is Aife, also making it seem that she and Dyson had met before. Aife drains Dyson of his energy as they have sex and drops him to the ground as Bo arrives. The two fight, but it's obvious that Aife is significantly stronger than Bo. Aife tries to explain how she's trying to help Bo, but Bo stabs her in the stomach with a broken chair leg. Aife removes it and limps away, later healing herself using her succubus powers. In the mean time, Bo manages to revive Dyson by giving him some of her energy like Aife did as Saskia before hand.
Aife is shown to be fully healed that night, and she goes to try to persuade a Light Fae Elder to join her rebellion, though he refuses. She has him killed and Aife and her Thralls carry on with their plan to start another war.
After Bo learns that Saskia is Aife and Aife is her mother, she's furious and goes to Trick for answers. In the meantime, Aife breaks into Bo and Kenzi's home, and bakes some cookies, with an unknown drug baked into them. As Bo comes home, Aife gives her some of the cookies, knocking her out and kidnapping her.
Bo wakes up in Aife's mansion, surrounded by her Thralls. She goes to find Aife who explains what Trick and the Dark Fae had done to her in the past, and how she had been searching for Bo for a long time now. Aife then asks Bo to join her in her act of rebellion, though Bo refuses, and Aife and her Thralls surround her, not allowing Bo to leave, though she escapes through a window and goes home.
In the meantime, Aife had sent one of her thralls, (who are revealed to all be Fae instead of brainwashed humans) as a suicide bomber to destroy the Light Fae Elders during a meeting between them and The Ash at his compound. It successfully assassinates some of them, while leaving others , such as The Ash, in critical condition, forcing them and the Noble families into seeking safety.
In Blood Lines, Lauren tells Bo about the Koushang in The Ash's vault so that she can use it to protect herself from Aife's chi-draining power. Kenzi accompanies Bo and finds it. Bo tests the Koushang's power on Kenzi and then hand-cuffs her to a pole to keep Kenzi at a safe distance from her battle with Aife. As Bo goes to confront Aife, Dyson goes to The Norn to supplicate a favour from her (for the second time in his life) to help Bo. He offers The Norn his "Wolf" in exchange for giving Bo his strength to fight Aife with, and The Norn grants his request, but realizing that what he no longer valued the most was his Wolf, she tricked Dyson and took his ability to love Bo or anyone else, instead.
Bo and Aife fight with spears and swords, Bo is disarmed and Aife attempts to drain her chi, but the Koushang blocks her power, giving Bo time to escape. Aife catches up to Bo and starts to choke her. Bo gets the upper hand against Aife as the act by The Norn takes effect, and she ends up hanging off the ledge from the top of a circular staircase, dangling above the ground below. Bo grabs her by the wrist and tries to pull her up but is unable. At the same time that Bo and Aife were fighting, Trick had begun to write with his blood and changed destiny, making Aife's maternal instincts emerge and stopping her from hurting or killing Bo. Aife releases her grip on Bo's hand and lets herself fall to her death from the top of the staircase.
Aife falls seemingly to her death, but when Kenzi and Bo reach the ground floor, a small puddle of blood is all that remains, and a male figure is shown carrying the unconscious and perhaps-dead Aife in his arms.
In Those Who Wander, a captive Aife reveals to Dyson that Dr. Isaac Taft was the male figure that had carried her away, and taken her to his private laboratory where he tortured Fae and conducted experiments on them. As a result of Taft's torture, Aife became almost catatonically insane, often babbling randomly in her cell, with her clearest comments being to beg for her daughter's safety, and warn about the punishment that would be inflicted by her daughter's father against Taft and his accomplices.
Having escaped Taft's compound at the end of Season 3, Aife appeared in In Memoriam with her sanity restored, now simply a concerned mother looking for her lost daughter, Bo, after all memory of what she had been was mysteriously erased. When Trick learned about her presence he went looking to find Aife and their reunion was warm, with her calling him "Daddy"; but just then the sudden restoration of everyone's memories of Bo resulted in Aife going mad again, she became enraged against Trick, and lunged at him with a knife.
Not much is known about her personality before the peace truce between the Light and Dark clans, but it could be assumed that Aife was a nicer and kinder person before then. However, after the killing of her mother, Isabeau; the betrayal by her father, The Blood King; being imprisoned for centuries by a Dark King, tortured and raped during such time; and using her blood to enslave victims to her will – she became evil.
She is sadistic, taking great pleasure out of seeing her victims suffer, particularly her enemies, and has a deep hatred for her father Trick (The Blood King). Though despite her now being deranged, in her own way she generally cares about her only daughter, Bo (Ysabeau).
Her age and experience also make her very powerful in comparison to Bo.
- "Hate's like beauty, baby. The real stuff fades, but it never dies. – to Bo (Blood Lines)
- "If your father was here, he would kill them all! And then resurrect them and then kill them again!" – to Bo (Those Who Wander)
- "Hi, daddy. It's all that I have left. It's all that's kept me alive. It's my hate. Knowing one day we would have our reunion and it would end in you spilling your cursed blood. (gives out a yell) This is for her!" – to Trick (In Memoriam)
- Aife reveals that succubi are big in Berlin, as they choose "sexier cities" and that she travels from city to city a lot.
- Aife went under the alias Saskia so that if she was ever mentioned by Bo then she wouldn't be recognized as Aife, but it is unknown why she chose the name Saskia.