We know the Room of Requirement can do magic. Like digging a magical tunnel from the fifth floor to Aberforth's pub. Or creating objects like the whistle.
So why didn't they wish the Room of Requirement to put the flames out?
We know the Room of Requirement can do magic. Like digging a magical tunnel from the fifth floor to Aberforth's pub. Or creating objects like the whistle.
So why didn't they wish the Room of Requirement to put the flames out?
The Room wasn't just on fire, it was on Fiendfyre, an extremely powerful curse.
"It must have been Fiendfyre!" whimpered Hermione, her eyes on the broken piece.
"Sorry?"
"Fiendfyre-- cursed fire-- it's one of the substances that destroy Horcruxes, but I would never, ever have dared use it, it's so dangerous." (DH: 31)
Fiendfyre was one of the few substances that was demonstrated to be able to destroy a Horcrux, which we know requires it to damage something beyond magical repair.
"So does it say how to destroy Horcruxes in that book?"
"Yes," said Hermione, now turning the fragile pages as if examining rotting entrails, "because it warns Dark wizards how strong they have to make the enchantments on them. From all that I've read, what Harry did to Riddle's diary was one of the few really foolproof ways of destroying a Horcrux."
"What, stabbing it with a basilisk fang?" asked Harry.
"Oh well, lucky we've got such a large supply of basilisk fangs, then," said Ron. "I was wondering what we were going to do with them."
"It doesn't have to be a basilisk fang," said Hermione patiently. "It has to be something so destructive that the Horcrux can't repair itself. Basilisk venom only has one antidote, and it's incredibly rare--"
"--phoenix tears," said Harry, nodding.
"Exactly," said Hermione. "Our problem is that there are very few substances as destructive as basilisk venom, and they're all dangerous to carry around with you. That's a problem we're going to have to solve, though, because ripping, smashing, or crushing a Horcrux won't do the trick. You've got to put it beyond magical repair." (DH 6)
It stands to reason then that if even Voldemort's charms can't repair damage from Fiendfyre, the Room of Requirement would have trouble with it.