Luna Thorne

''Is that what it’s like, to be a mother? Is that what it’s like to be in love?''

Luna Thorne is a secondary antagonist (amongst other things) in Mabel. Her voice actress is never credited, though it can be assumed she is played by Maybell Marten.

Season One
Luna Thorne is many things, and none of them are simple to summarize. One concrete fact is that Luna is the girl in Mabel Martin's mirror; her face is scarred on the side opposite to where Mabel's is. They spoke often when Mabel was a child, until an incident when Mabel was bitten by a fox; she and Luna then began fighting, to the point where Mabel would either cover or break every mirror in the House in order to avoid seeing Luna.

Around 2016, Anna Limón discovers a box of letters from Luna in Sally Martin's attic. Each letter is sealed with a kiss. When Sally is taken to the hospital, she tells Anna she had tried to save Luna, years before. Anna later speculates that Luna was the "hare of the moon" and the woman who had "bad, bad fortune" in the various writings she had found throughout The House. In The Freeze, Luna comes to the House to take Anna down under the hill.

Season Two
Anna says that when she was brought into the Underhill she was not able to look Luna in the eye. We also learn that Luna was the consort of the King; she is commonly referred to as his pet in story canon. Mabel again mentions breaking the mirrors in order to hide from Luna again in Killing the Moon.

Seasons Three & Four
In Unusual Hungers, Mabel tells Anna the story of Luna; she was, at some point, created (as the moon) in order to (complicatedly?) combat and feed the darkness. At some point, Luna and Sally met and became close. Sally did not truly understand Luna, however, and at some point, Sally-- overwhelmed by the thought of leaving her entire life behind-- ran from Luna and married her husband. Sally thus broke her promise to save Luna, and left Luna to rot in the Underhill.

Within season three, Luna creates Veratrine to take Anna's place in the upper world. When Anna, Mabel, and Veratrine travel to the Court, they find Luna kneeling at the foot of the King; Veratrine, terrified, explains that she usually spends her time beating at the bars of her cage. With Luna now as a model inmate, the trio of irreverent miscreants quickly realize they need to escape back to the House.

Luna and Veratrine have dueling narratives in Matryoshka; it is revealed to the audience at this point that Luna created Vera. She asks if creating Veratrine is, in two senses, like being a mother or like being in love. It is also revealed that the King found Luna in a field of flowers.

Luna and Veratrine have a discussion in Temporal Snake; it ends with the two of them deciding to run away together.

Season Six
Luna presides over Anna's coronation to Kingship; she is the speaker/preist who has Mabel pledge herself to Anna. Anna and Mabel discuss Luna and the King's relationship, and it is revealed that they were in no way romantically involved with each other, their relationship more resembling a business partnership. She broke a promise, and the King held her to it. That is all.

Luna Thorne is dead; long live Luna Thorne.

Season Seven
Veratrine says that Luna has been "torn apart and torn asunder". It can be assumed they've broken up.

Trivia

 * As Luna's partner, Veratrine, is written by Maybell Marten, it can be assumed that Luna is written by Becca De La Rosa. While this has never been confirmed, it does explain why Luna's monologues resemble Anna's moreso than Mabel's.
 * According to King in the Labyrinth and Reverie, Luna has scars all over her face.
 * Luna, as the girl in Mabel's mirror, took the place Anna should have had (as usually, the love of the Martin girl's life is in their mirror. See Juniper).
 * She has some fondness for Mabel, as is clear in season six.