- "The Hardening Charm will turn an object into solid stone. This can be surprisingly handy in a tight spot. Of course, most students only seem to use this spell to sabotage their fellow students' schoolbags or to turn a pumpkin pasty to stone just before someone bites into it. It is unwise to try this unworthy trick on any of your teachers."
- —Miranda Goshawk, Book of Spells.[src]
The Hardening Charm (Duro) is a charm used to change objects into stone. Hermione Granger cast the spell at a tapestry during the Battle of Hogwarts, turning it into stone and wounding the two Death Eaters who were pursuing her, Harry Potter, and Ron Weasley.
Duro is Latin for "I harden" or "I stiffen"; the same term is Portuguese for "hard" or "rough"; it makes sense given J. K. Rowling's relation to the language.
- Harry Potter and the Deathly Hallows (First appearance)
- Wonderbook: Book of Spells (First identified as Hardening Charm)