Meteora Butterfly

"My daughter had pretty little clovers on her cheeks, and the cutest tail in all of Mewni"

- Eclipsa Butterfly

Meteora Butterfly (better known as Miss Heinous) is the tertiary antagonist of Star vs. the Forces of Evil. She was the headmistress of St. Olga's Reform School for Wayward Princesses and is the Mewman/monster hybrid daughter of Queen Eclipsa.

Background
Before she was born, Meteora's mother was wed to a Mewman king, but was already in love with a monster named Globgor. Eclipsa later eloped with this monster and gave birth to Meteora, becoming the first Mewman/monster hybrid. Because she was part monster, the Magic High Commission saw Meteora as a threat to magic and Eclipsa's ex-husband, King Shastacan, did not want anything to do with her. She was replaced by the Magic High Commission with a peasant girl named Festivia and all record of her was erased from the Royal Archive.

Meteora was then sent to be raised by St. Olga, the robot headmistress of St. Olga's Reform School for Wayward Princesses, where rebel princesses were "reformed" into "proper" princesses with no individuality. Meteora was taught to hide her monster traits and be proper; but whenever Meteora displayed any unconventional behavior and traits, St. Olga strapped her to the school's reconditioning "Solitary Conform-ment Chamber" to brainwash Meteora into forgetting her true identity. Sometime after St. Olga was deactivated, Meteora took over the school as Miss Heinous and continued her foster mother's "reformation" methods. She remained young by draining the youth of other princesses for 300 years.

Role in the series
Miss Heinous debuts in the episode "St. Olga's Reform School for Wayward Princesses" instructing the next batch of princesses enrolled into her school. In the climax of the episode, she loses control of the school when Marco Diaz and Star Butterfly rallied a rebellion while trying to rescue Pony Head. After that, she swears revenge and sought to destroy them both at all costs.

Miss Heinous leaves St. Olga's to pursue Marco and Star and arrives at Earth with her assistant Gemini. They are shown living in a rundown apartment while residing on Earth. Heinous also hires the bounty hunter Rasticore to attack Star and Marco with no success, as Rasticore's hand is delivered back to Miss Heinous following his destruction. After finding out that "Princess Marco" is a boy, Miss Heinous tries to use this information to get control back over her school, confident that the girls' faith in "Princess Marco" will shatter and will rely on Heinous once again. However, the students chase her off once again.

In "Monster Bash", Miss Heinous starts losing her youth so she tries to steal Marco's youth. After infiltrating an old Monster Temple, where Star was hosting a party to celebrate the unity of Monsters and Mewmans, Heinous rediscovers her old nursery and remembers her true name and heritage as Meteora. Escaping with her cronies, Meteora starts manifesting traits of her monster heritage as she discards the Miss Heinous name. Returning to St. Olga's in "Skooled!", Meteora confronts the remains of St. Olga to uncover what happened to her lost memories. After realizing how she lost everything because of the Butterfly family, Meteora destroys St. Olga and becomes more monstrous, demolishing the students' forces and ripping off Pony Head's horn as she leaves St. Olga's. Meteora also tears out Gemini's robotic heart and blows up Rasticore's body, reducing him to an arm again, as she heads out to reclaim the Mewman throne.

By "Tough Love", Meteora has unlocked her magical powers to start absorbing souls from anyone who crossed her, causing her to become a monstrous giant. As she heads towards the kingdom, she is found by Queen Moon Butterfly and Eclipsa. Eclipsa tries to reason with Meteora but fails and Moon attacks her. The fight leaves Moon damaged, and she flees as Meteora continues on her way. Marco and his allies also try to hold Meteora off, but only succeed in hindering the monstress' rampage and she takes their souls as well (except for Tom Lucitor due to possessing many souls). Meteora then invades Butterfly Castle, having absorbed almost all the souls of everyone else on Mewni (except for Star and Tom). When Tom arrives with a soulless Marco, Meteora captures the boys while Star arrives after to confront Meteora. After an intense battle, Star damages Meteora at the cost of a huge magic drain. Eclipsa then appears and borrows Star's Royal Magic Wand to overwhelm Meteora. With her dark magic, Eclipsa reverts her back to a baby, which frees all the souls Meteora has absorbed. Eclipsa then departs with Meteora to travel back to the temple where her monster husband, Globgar, is to reunite the three.

Trivia

 * According to Star and Marco's Guide to Mastering Every Dimension, Miss Heinous is an inter-dimensional fugitive wanted by the Magic High Commission.