As a descendant of the Sullivan family, scions of the quasi-Spiritualist New Albion Association and increasingly distant relatives of famous local medium Charity Sullivan, Mercy (as she prefers to be called) was raised from a young age to accept the reality of the supernatural and embrace her own psychic potential. She did that quite readily -- but by the time she hit adolescence and her powers began to manifest in earnest, the young woman had come to realize that, as a known psychic, she would be effectively imprisoned by her parents and their organization, kept under close scrutiny at all times and compelled to do their will. Mercy rejected this idea out of hand, and did her best to disguise her powers, encouraging her younger sister to do the same. The ploy worked, as both were passed over by the Association and given a good deal of personal freedom. Once she'd graduated from the private boarding school she attended in London, Mercy set off for the city of her birth, enrolling at Greyson University and taking up the fight against the forces of darkness on her own terms.

In the weeks leading up to her orientation, Mercy began to dream of a mystically empowered, remarkably strong champion, a young woman who fought monsters and defended the ordinary people of Shadowgard from occult forces. When she met her freshman roommate, Taryn Maddock, the dreams started to make sense -- but nevertheless, she continued to hold her tongue, until they were finally attacked by a gang of vampires and Taryn was forced to reveal her nascent abilities. Since that time, Mercy has become a loyal friend and ally, using her ability to reach out to the dead to help the rest of the group find some measure of clarity in their lives, and guiding them all through her existing knowledge of the occult.

An outgoing, intelligent, somewhat loud and occasionally blunt girl, Mercy is actually quite tender toward the people she knows and cares about, her casual flirtiness masking a center that's somewhat more shy. She cares fiercely and deeply about her loved ones, and in particular, she's very affectionate and protective toward her little sister, frequently struggling with their current separation. The young woman also displays remarkable insight and an ability to take in the whole of any given situation all at once. Her wide perspective tends to lead to a serenity and gentle fatalism that the others find alternately reassuring and infuriating. It falls to other members of the gang to serve as the mind, the hand, even the heart of the group, but to at least some degree, Mercy is the mystical and spiritual center.