Padma Patil, who was Parvati's twin, but had sorted into Ravenclaw instead of Gryffindor, looked in disgust at her sister and raised her hand.
"Yes, Miss Patil?" said Professor Moody.
"Won't we know exactly what curse is being used on us when we hear the incantation?" she asked.
"An excellent point," said Professor Moody as he turned to face her, while keeping his one magical eye trained on Parvati and Lavender. "Any competent enough Wizard, Dark or otherwise, can cast a spell without saying its incantation out loud, to take their opponent by surprise. The spell won't be as potent, but it can and will still hurt you, leaving you open to further attacks, which is why you need to be able to recognize what magic is being cast at you."
"…"
"CONSTANT VIGILANCE!" barked Moody, startling the class once more.
"…!"
"So … do any of you know which curses are most heavily punished by wizarding law?" he asked after a while.
A few hands rose into the air, including Ron's, to Oleandra's surprise. Ron almost never participated in class actively of his own free will!
"Er," said Ron tentatively, "my dad told me about one... Is it called the Imperius Curse, or something?"
"Ah, yes," said Professor Moody, nodding knowingly. "Your father would know that one very well; it gave the Ministry a lot of trouble a few years back, the Imperius Curse."
Professor Moody placed a glass jar on his desk, in which three, big, black spiders had been trapped. They didn't seem interested in fighting each other, despite being enclosed in a tight space together.
"Hello!" Moody cooed at one of the spiders as he retrieved it and let it walk on his open palm. "Imperio!"
Oleandra looked on with interest; it wasn't every day one got to see one of the infamous Unforgivable Curses. Even though it was only illegal to use them on other humans (which included Muggles), most people steered clear from them, and for good reason: Dark magic was just bad for your mental health.
Moody waved his wand like he was conducting an orchestra, and the spider followed his every order, even getting up on its two hind legs and beginning to tap dance. Everyone laughed at this performance— even Ron, who didn't seem to like spiders very much.
"Think it's funny, do you?" he growled. "You'd like it, would you, if I did it to you?"
The mood of the class instantly turned ice cold. No, it turns out it wouldn't be very funny if such a thing happened to them.
"Total control," Moody said quietly, as he made the spider curl up into a ball and roll around like Sonic the Hedgehog. "I could make it jump out the window, drown itself, or even throw itself down one your throats."
The problem with the Imperius Curse was that it left no sequelae. If one were particularly attentive, it was possible to identify someone who was under another's dominion while the Curse was active, but once control was relinquished, it became impossible to determine whether someone had done things of their own free will… or if they'd been under someone else's control!
As such, when Lord Voldemort had been at the height of his power, his chief weapons had been to sow the seeds of distrust, to create an aura of fear and to generate despair, all to divide and conquer! It had almost been too easy…
"The Imperius Curse is the only one of the three Unforgivables that can be resisted, but it takes real strength of character. Unfortunately, not everyone's got an unbending will. As with all curses, better to avoid being hit with it in the first place."
"…"
"CONSTANT VIGILANCE!"
"…!"
"Since we're on the subject of the Unforgivable Curses, who can name me another one?" Professor Moody continued.
To Oleandra's surprise, even Longbottom raised his hand this time. Did he have something to get off his chest? She had never known him to raise his hand in class, like, ever.
"Yes," said Professor Moody, looking straight at Longbottom.
"There's one— the Cruciatus Curse," said Longbottom quietly, yet not timidly.
"Longbottom, is that right?" Professor Moody said, checking the class register with his magical eye.
Professor Moody plunged his hand into his jar and retrieved a second spider. This one, however, did not seem well at all. How many times had he used this spider to demonstrate the Cruciatus Curse?
"Hrngh," grumbled Professor Moody. "Needs to be a bit bigger to give you a proper idea. Engorgio!"
Ron's chair audibly screeched against the floor as he pushed himself as far away as he could from the embiggened spider. Not that he had anything to fear; the spider knew this was the prelude to something terrible, and it was bracing itself for what was to come.
"Crucio!" muttered Professor Moody, pointing his wand at the quivering spider.
A low hissing sound, like that of air escaping a balloon, could be heard over the absolute silence that had fallen over the class. Oleandra realized it was the spider's way of screaming; it was rubbing its barbed pedipalps against each other, producing this wretched sound. Nobody else seemed to have noticed its quavering cry, though.
"Stop it!" Hermione said shrilly after a while. "Can't you see it's bothering him?"
She was talking about Longbottom, rather than about the spider. Longbottom had seized up, frozen in horror. The spider wasn't doing so well either, thanks for asking.
"Reducio," said Professor Moody softly, reducing the spider back to its previous size and storing it back with the others. "The Cruciatus Curse, the torture curse. Very popular, once upon a time. No need for thumbscrews or knives to torture someone if you can perform this one."
Oleandra begged to differ: knives still very much hurt, and she could still feel the phantom pain aching from time to time. She looked at her hands under her desk, remembering the painful memories of how she'd been turned into a marionette without strings.
"How about you, Miss Greengrass?" said Professor Moody, ignoring Hermione's outstretched hand. "Got something interesting to show us under that desk? Or was there something you wanted to say?"
The last of the Unforgivables was quite famous; there was no Wizard-born child who didn't know about it.
"The Killing Curse," Oleandra said distractedly, putting her hands back on her desk. "Instant death magic. Under which principle does it operate?"
"There are a thousand spells that can injure enough to kill," said Professor Moody darkly, "but there is only one Killing Curse. It has no Counter-Curse, because unlike most injuries, there is no coming back from the dead. This is beyond N.E.W.T. level magic: conceptual magic. It doesn't need to choke you, drown you, destroy your vital organs, incinerate you, bleed you dry, or separate your soul from your body to kill; if you are hit by this Curse: you will die. It penetrates all magical defences like butter, and it only stops when it finds something to kill, or something inanimate that it can't kill. To be able to cast it, you must have the will to kill."
Professor Moody retrieved the last spider from the jar and placed it on his desk; this one seemed in good spirits. And at that moment, Naudhiz, the rune of distress, gave a warning buzz in Oleandra's mind palace unlike any it had ever given before. Cloak instinctively reacted to Oleandra's heightened emotions and covered as much of her as it could.
"Avada Kedavra!" Professor Moody roared. A green light flooded out of his wand and the sound of rushing wind was heard, even though they were indoors. And the spider lay dead on his desk.
CRACK!
Oleandra looked down; she had inadvertently dug ten long grooves in her wooden desk with her fingers. She had clutched her desk so forcefully with her hands, which were empowered with part of her Lethifold disguised as her gloves, that she penetrated the lacquer and the wood. Padma Patil looked at her suited-up form in alarm.
"There is only one person in the history of Wizardkind to have survived the Killing Curse," said Professor Moody, looking straight into Harry's eyes. "And he's sitting right in front of me."
"…"
"CONSTANT VIGILANCE!" he roared again, interrupting the shocked silence.