After a week of anticipation (and apprehension for me), Griffindors finally have a class with the famous Auror Alastor "Mad-Eye" Moody. Although Professor Lupin set quite a high bar for DADA, there's much to be optimistic about in most student's eyes.
From the books, Moody's class consisted of quite practical dark magic defense, as he was a Death Eater in disguise. Unforgivable Curses are not often seen or experienced (Crucio could potentially induce insanity and Avada Kedavra literally causes death), and learning about them from the Restricted Section would definitely send a glaring signal to Dumbledore, so a safe environment to fight off Imperio would be welcome.
That said, just to be safe than sorry, I turned to my mind space and asked:
"Are there any items that can resist Imperio? If possible, permanently?"
"May I assume Magneto's helmet is out of the question?", replied the voice, having known my (lack there of) magical accomplishments and therefore inability to hide such an obvious physical item.
With a metaphysical nod from me, the voice continued:
"From my knowledge, Viktor's Neural Neutralizing Drugs could remove uncontrollable impulses as well as any chance of Imperio being effective - though a permanent dose would also render the user emotionless. I would suggest an on-demand injection before experiencing the curse - it's your choice, sir."
"Set the dose just as you said.", I replied before returning to the classroom where myself, Hermione and Ron were settling down for our first DADA lesson. Before long, the signature clank-clank of the prosthetic leg echoed out the doors.
"Constant Vigilance!", shouted the impersonator as he strode into the room as all students jumped up in surprise - Neville helplessly falling on his back.
"If I were a Dark wizard, most of you here will not be alive by now. Obviously, your previous professor did not adequately prepare you for this subject. Now, who can tell me what you learnt last year?"
Seamus, or Dean, I cannot tell, raised his hand timidly.
"Professor Lupin taught us Red Caps, Boggarts, Hinkypunks, Grindylows, Kappas and Werewolves..."
"Quite thorough at Dark creatures, eh? However, this class is behind - very behind - on curses," said Crouch. "And so, for one year, I am to show you up all the nasty things wizards can do to each other - otherwise known as the Dark Arts."
At these words, several students from wizard families, namely Neville and Ron, showed both fear and hesitant curiosity, choosing to listen raptly. The Professor paused, his magic eye swirling around the classroom and continued seriously, if somewhat reverentially:
"Now, a common misconception of Dark magic is that it's inherently evil and powerful. Like all magic, be it a trivial hex or the most gruesome curse, depend on two factors: the emotions of the caster and their magic power. Any of you lot know the Severing Charm?", he asked, surveying the rows of students and having no choice but to call out a quivering, lightning-fast hand.
"Go on, Ms... Granger.", Crouch pronounced, visible distaste showing in his frown.
"Yes sir, we learnt it this week. Professor Flitwick said it's quite a handy spell at tailoring", my bushy-haired girlfriend answered quickly.
"Quite accurate. A point for Griffindor.", The compliment earned a smile from Hermione. "However, what he probably did not tell you Diffindo can do this -"
At the spell, Crouch pointed at the empty desk in front and cleaved it clean in half. The class went silent at the splintered wood strewn across the floor and shuddered at its power. The disguised Death Eater is not finished, however, as he mended the table and demonstrated again.
After confirming everyone's attention is back on him, Crouch muttered the spell again and flicked his wand, this time a palpable chill gleamed in his eyes. The same gash split the desk, yet this time, wood closer to the mark started to decay until all's left of the object is a pile of dust on the floor. Crouch attempted to mend it, but the dust barely started to coalesce before disintegrating once more.
Not discouraged, the Professor turned to the astonished Griffindors:
"The same mundane spell Ms Granger mentioned, the first with power, and the second combining intent. Now, Hogwarts would not teach you these - but Dark Wizards won't let down their hand because of sportsmanship. Wiser men than you have lost limbs, eyes or even their lives for underestimating those basic spells - trust me, you can't afford to do the same even if they seem the simplest, got it?"
Just as students start nodding in contemplation, Crouch roared, causing the whole class to jump:
"Constant Vigilance! What are you dawdling for? Get your quills out and copy this down!"
The rest of the class were spent on seemingly mundane but quite terrifying modifications and applications of spells such as Reparo or Aguamenti - which, rightfully so, made me consider the Death Eater in a new light. It seems that Barty Crouch has a rather solid magical understanding and teaching skills, though it is a shame he's on Voldy's side.
No one doubted the Professor's ability when the bell rang - only after dismissing the class and giving "Three-feet essay on possible defense applications of known spells" as homework did the suppressed conversations burst forth. Most people with better theoretical knowledge - namely, Hermione and me - saw the lesson rather positively.
"Did you see the second spell, Harry?", Hermione caught up and said. "I'm sure Professor Moody was great back in his Auror days, I've been trying spell modifications for years and it never quite worked..."
I nodded contemplatively, "Do you think curses and jinxes are no different except for that intent? Come to think of it, even transfiguration could be quite nasty, used offensively..."
"Transfiguration...Wait! Wouldn't that mean the Werewolf curse is just an extremely powerful version of human transfiguration?...Magic and Dark Arts must have a common root, Harry!", she exclaimed.
While some (the two of us) were overwhelmed with this revelation, Ron was talking to other Griffindor boys, apparently not finding most of it entertaining but for the strength display- this sentiment resonated with the rest of them. Hermione and I walked ahead to lunch and later library, where I subtly led us to learn Unforgivable curses in preparation.
For different uses of Diffindo, I base this on its similarity with Sectumsempra (Snape's spell) and the many variations of Lumos (Maxima, Dumbledore's Put-Outer) as well as Protego (Horriblis - Grindelwald's Blue Flames in second Fantastic Beasts movie)