She was passionate, talented, and stubborn, just like you.
Harry telling Mel about his previous charge

Fiona Callaghan is a witch and younger sister of Charity Callaghan; and former charge of Harry Greenwood's; both of whom believe she is dead.


Fiona revealed her magic to the wrong mortal. She was subsequently institutionalized and came to believe that she was insane, rather than truly possessing magical abilities. She was said to have committed suicide until it was revealed that she was alive and a member of The Sisters of Arcana in late 2018.

Throughout the episode "Bug a Boo", it was strongly hinted that Fiona was not institutionalized, but actually imprisoned in Tartarus by the Elders for her affiliation with the S'Arcana, until Jada released her with the Scythe of Tartarus.