"That was a really horrible trick of Hermione Granger's. ...She should have told us she'd jinxed that list -"
-- Cho Chang defending her friend Marietta (OP28)
A delayed-action jinx which writes the word “sneak” across someone’s face in pimples if they break an agreement they sign. This jinx may be an invention of Hermione Granger.
References from the canon
- Hermione jinxed a piece of parchment with this spell. Each member of the D.A. signed the parchment when the group started meeting and in so doing put themsleves under its effect. When Marietta Edgecombe told Umbridge about the D.A., the word "sneak" broke out on her face instantly. Umbridge tried to remove it but couldn't, which indicates just how talented Hermione is at casting spells (OP16)
- This jinx was still in effect on Marietta the following September (HBP7) However she probably could not remember why she had the pimples, since Kingsley Shacklebolt put a memory charm on her to make her forget what she knew about the D.A.(OP27).
Jinxes and hexes
Many readers were as disturbed as Cho Chang that Hermione used such a strong jinx to protect the secrecy of Dumbledore's Army, and especially to disfigure another girl's face in such a long-lasting way. However, one of Rowling's main themes has always been that of loyalty to friends and to the cause of justice, and Marietta Edgecombe was the Peter Pettigrew of Harry's generation. She was just a tag-along to the D.A. meetings, showed little interest in learning to fight, and had little faith in Harry. While it was true that Marietta felt pressured by Umbridge because her mother worked at the Ministry, the same could be said for the Weasleys, as Harry pointed out to Cho. While many readers may fault Hermione for going a bit overboard with her jinx, Marietta's injury was less disturbing than what Harry and others suffered from Umbridge's painful black quill.