Seth, also known as Seth of Septarsis, is the posthumous overarching antagonist of Star vs. the Forces of Evil. Despite only appearing in the book Star vs. the Forces of Evil: Magic Book of Spells, his actions paved the way for most of the events in the series.
Seth is the oldest Septarian with a long hatred of Mewmans and wished to eradicate them from Mewni.
According to Globgor and Eclipsa, he is often described as an extremist and likes to hold a grudge for centuries much like the rest of the Septarians. Moreover, Comet Butterfly described him as an old and decay monster with a decaying and rotten hatred and ideas but dangerously attractive to the young generations of the Septarians. Most of the peaceful monsters reviled and feared him as even Globgor, the Prince of Darkness, calling him troublesome and despicable. Furthermore, he is also the reason why Eclipsa developed the darkest spell to combat his race.
During the conflict between Mewmen and Monsters and the reign of Star's grandmother, Comet Butterfly, he led the monster faction that opposed the peace treaty made by Comet Butterfly and Archduke Batwin. When Comet tried to invite him to the banquet to settle the conflict peacefully, he declined and wanted her dead.
He died prior to the events of the series, but the impact of his actions kicked off the plot of the show.
- It is speculated that Seth is the power behind Toffee's action in killing Comet Butterfly.
- Seth's appearance somewhat resembles Rasticore.
- Seth's face resembles that of a crocodile.
- Despite appearing in the book, Seth never appeared nor was mentioned in the series itself. The reason for this is because he's dead.
- Daron Nefcy, the serie's creator, confirmed in an official AMA that Seth died prior to the events of the series.
Toffee | Ludo | Meteora Butterfly | Mina Loveberry | Tom Lucitor | Gemini | Rasticore | Seth | Giant Spider | Bald Eagle | Buff Frog | Bearicorn | Beard Deer | Three-eyed Potato Baby | Big Chicken | Two-Headed Monster | Giraffe Monster | Boo Fly | Lobster Claws | Warthog Monster | Crocodile Monster | Frill-neck Monster | Lizard Monster