system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Is Fiendfyre a difficult spell, difficult to find a teacher for, or something else?

I find it very strange that the only person to use such a powerful spell in the entire series struggled with his magical studies and showed no particular aptitude for casting spells compared to his peers.
gpt
No.

Fiendfyre isn't a difficult spell, not in terms of ability. Crabbe cast it, and he was thick as two bricks. It does require a bit of magical power, which Crabbe has through practice if nothing else - he can manage a Killing Curse, which according to Crouch requires a fair bit of power. Fiendfyre is a monstrously powerful spell and easy enough to learn. It makes up for that by being ridiculously dangerous. Crabbe died casting it. It consumed the entire Room of Hidden Things in minutes. It is simply too dangerous for anyone without enormous willpower and control to cast, if they have half an ounce of sense.