Fiona was born with her twin brother, Jackson, in 1888.  In 1910, following the death of her brother, Fiona was called by her family to take up the mask of the Hunter and destroy Demona (she was not the first woman to join the hunt).  Ten years later, she succeeded in tracking The Demon to Paris. Teaming up with her old flame, Joshua Sweet, and the rest of Team Atlantis, she attempted to stop Demona from destroying Paris and thus end the hunt once and for all. While Demona's plan to destroy Paris was thwarted, the hunt was not ended once and for all. This part of Fiona's mission was doomed from the outset, as only Macbeth can kill Demona. ("The Last")
As of 1996, Fiona was still living at the age of 108.  By this time she has largely retired as a Hunter.  Fiona no longer sees her family's mission of hunting gargoyles as being of paramount importance, describing it as "a vignette in a much larger tapestry", or, at least, that is what she told her niece Robyn Canmore. She is also a member of the Illuminati, and participated in an effort to recruit her niece and the rest of the Redemption Squad into the Society. ("Losers")
In 1920, Fiona was a tall, Valkyriesque woman with blond hair braided into a thick rope. She also has three small scars above her left eye, given to her by Demona. By 1996, she had aged much, but was hardly frail (possibly due, at least in part, to the rejuvenation drugs that the Illuminati give their older members). She still wore her hair in a thick braid and bore the scars above her left eye.