The previous Guardian of water before her death. She was succeeded by Irma Lair.
Cassidy liked swimming, and was on the Sheffield Institute swim team, the Sheffield Sea Slugs. Cassidy also liked going to the beach. She described Shell Beach as her favorite place in town. She mentioned she liked walking into the ocean, looking at cute lifeguards, and going for a swim. Cassidy had compassion for all living things and wanted to be a pediatrician.
When she regained her power and mortal form through Nerissa, her power was twice Irma’s power as it was fuelled by two Hearts. After Nerissa was trapped in the gem, she returned to her normal life.