Miss Heinous is the tertiary antagonist of Star vs The Forces of Evil. She wants to strictly control bad behavior in wayward princesses, forcing them to act like "proper" princesses with no individuality of their own.
In the second season, she becomes the arch-nemesis of the show's deuteragonist, Marco Diaz.
Debut and Appearance
As the headmistress of St. Olga's Reform School for Wayward Princesses, Miss Heinous makes sure her staff has the princesses attending her reform school be reformed into normal princesses. For particularly troublesome princesses, she uses the "Solitary Conform-ment Chamber," which forcibly brainwashes them into acting the way she wants them to. Despite her best attempts, Star Butterfly and Marco Diaz infiltrate the school and cause a revolt. After they leave, she finds out that they came from Earth and swears to annihilate them.