Mercy is the second daughter of Daeva and her husband. Sometime, when she and her twin sister, Bellatrix were four, Daeva made their father disappear. At first, she was given gifts from her mom until she was fourteen. Daeva tried to teach Mercy witchcraft like her twin, but she didn't want to kill anything so Daeva sent her to a foster home and refused to see her again.
Mercy was alone for a few years and when she turned eighteen, she left the foster home and discovered a recently abandoned theater and turned it into her home. Using the witch powers that she inherited from her mother, she grew a garden of vegetables and fruit, refusing to eat meat. To earn a living, she worked as an acrobat for a indoor circus company and part-time magician's assistant.
Every now and then, Mercy would prevent her mom and sister from taking children and the children that were taken and lost their lives, she would revive them. Mercy overheard her mom and sister working on a plan with Orick, Nazreen and the cooperation of Pitch, Rune, and Eric. Mercy followed them and helped saved the Guardians and their friend, Symphony. She spoke to Eric and convinced him that she can bring his late wife back. At first, Eric thought he was going to be tricked like what Daeva and Bellatrix did. However, Mercy convinced him that she was speaking the truth by letting the spirit of late wife, Marriane, speak to him and Eric believed her and gave her a tissue that Marriane owned. With the help of her powers, Mercy brought back Marriane and gave her a necklace of protection so she wouldn't get hurt from any ill magic. Mercy met Xavier, one of Symphony's brothers, during that time and for reason she gave him her number and then returned home.
Afterwards, she and Xavier would meet and go out to the circus where she worked.
- Mercy's mother that she is estrange from. Daeva expects absolute obedience from her daughters, but Mercy's refusal to kill, led to be sent to a foster home.
- Mercy's twin sister. They never got along with each other due to their different personalities and beliefs.
- Mercy's cousin. They did not get along when Mercy was still in the family.
- Guardian of Illusion. Mercy was a big fan of his late wife, Marriane, when she was singing. Mercy convinced Eric that she can bring back his wife and with the help of Marriane's spirit, she used her magic to restore her to life.
- One of Symphony's brothers. After saving Symphony and bringing back Marriane for Eric, she met Xavier and for some reason, unknown to herself, gave him her number. They had since developed a relationship together.
- Mercy is like her name; she spares people's lives and animals as well.
- Mercy is a vegetarian and grows her own food.