"You messed with the wrong family." ― Rhea to Neoma in Curtain Call
Rhea Evelyn Castillo (born Rhea Evelyn Vermont) is a supporting character of Ephemerality. She is the current Supreme Witch/Elder Witch of the Castillo Coven, the oldest and most powerful coven of all time whom descended from the Original Witch, Ambrose. She is the daughter of Iman Vermont and Phillip Carlson, the former girlfriend of Damien McCartney and Erik Santana, and the mother of Aurora and Donny Castillo.

Rhea was born and raised in Thornwood, and unlike her daughter, she was already aware of her abilities before she turned 18. It is mentioned that Rhea used to be the most popular woman in Thornwood, known for her beauty, intelligent, and bluntness. Because of this, Rhea gained the attention of Thornwood's most eligible, Damien McCartney. Rhea and Damien were a couple for 3 years before Rhea was forced to leave him due to the increasing risks of her new powers and threats. A year later, she meets Erik Santana, a young businessman-to-be from New York in a bar. They hit it off later and Rhea discovers she is of child. Yet, six months into a long distance relationship, Rhea discovers that Erik has a fiance, later breaking up with him.

In the beginning of the book, Rhea is a doctor in Thornwood Hospital. She is described to be protective about her children as Aurora never found out about the magic side of the family. She would later find out about Aurora's alcohol abuse and has a heart-to-heart moment with her in Delinquents.