John is a pink pony-like fiend of enormous proportions with sharp teeth and a floral pattern on its sides, and well as a striped tail and mane.
It is unknown what gender John is; Charlotte asked about its gender, and Vendetta, despite not really knowing for sure (suggesting that most, if not all her fiends are genderless), said it was a girl. Charlotte named "her" John. It terrorized everyone in the town of Clamburg, to the point where they'd even stay in Vendetta's house to avoid it. After they refuse to leave despite her warnings, Vendetta agrees to help. She goes out, and uses her Eagle fiend to fly the pony away.
In "Pony", Charlotte repeatedly asked Vendetta to create a pony for her to play with, constantly drawing and giving Vendetta pictures of the ideal creature. At first, Vendetta was simply annoyed by this and tried to ignore Charlotte, but after a while, she she decided to use this as an opportunity to destroy Charlotte, and she created a pony fiend based on one of Charlotte's pictures.