Britain, Scottish Highlands.
In a remote area shrouded by several kinds of Protective Magic, Harry was intently waving his wand, practising the Fiendfyre Curse he had learned from Mad-Eye Moody. He lit the simple fire pit before him and tried to control the black flames, keeping Fiendfyre from spreading in every direction.
To Harry's left, Hermione and Ron gripped their wands nervously, ready at any moment to use the Counter-curse Moody had recently taught them to extinguish the Fiendfyre in the fire pit.
Unfortunately, all three of them failed.
Shortly after Harry finished casting the Fiendfyre Curse, the black magic fire turned into roiling waves of flame, showing signs of losing control as it began to spread beyond the fire pit.
Once the black Magic Flame spilled out of the fire pit, Ron and Hermione swung their wands at the same time, using the Counter-curse Moody had taught them to try and suppress the out-of-control Fiendfyre.
However, they only managed to suppress the black Magic Flame slightly and could not stop Fiendfyre from spreading.
In the end, it took several Order of the Phoenix members around them acting together to completely contain the roiling black Fiendfyre and put it out shortly afterward.
"Failed again."
Harry could not help feeling discouraged. This was already his third day practising the Fiendfyre Curse.
Unfortunately, the difficulty of advanced Dark Magic was far beyond anything they had imagined. Despite all their effort, they had made little progress.
Summoning Fiendfyre was not difficult at all, but controlling it was. Once it appeared, it quickly ran completely wild, spreading, expanding, and devouring everything in its path.
Even the Counter-curse Ron and Hermione were practising had little effect on Fiendfyre, as though the counterspell itself were fake.
"I really don't understand why you insist on learning such