Mantock will play Macy, a practical, driven, and brilliant geneticist who has her world blown open when she discovers that the supernatural world is all too real.
The actress joins the previously cast Melonie Diaz, with one last sister character still to be cast. Jeffery will play Madison, described as a bubbly college freshman who finds witchcraft at odds with her goal of getting in to a super fun sorority.
Diaz will play Mel, one of the three sisters who is described as a passionate, outspoken activist who loses her way in the wake of a family tragedy.
Guy Pearce is set to star in the newly titled eight-episode supernatural drama series The Innocents.
The new Charmed is described as a fierce, funny, feminist reboot of the original series, which centers on three sisters in a college town who discover they are witches.
The CW is adding a reboot of the popular supernatural 2000s show CHARMED to its development slate, with the Jane the Virigin team at the helm. It has been given a script commitment.