Professor Snape remained steadfastly silent on the walk from the Great Hall's dueling arena down to the dungeons.
It wasn't until they entered the gloom and damp of the cellar that Snape abruptly stopped.
"Hexes, jinxes, curses... you've learned quite a few..."
He spoke in a low voice, his hooked nose looking exceptionally sharp under the dim dungeon lights.
"Thirty-six hexes, eighteen jinxes, and six curses, Professor," Sean nodded.
"Heh..."
Snape let out a cold sneer, betraying a trace of anxiety that was suppressed almost to the point of invisibility.
"Barely a passing grade. But—
"In terms of countering spells, your education is woefully inadequate. Woefully. This will be your first lesson, and perhaps your last.
"Today, you will witness how wizards truly operate. I will dedicate sufficient time to teaching you how to deal with..."
He paused there, simply staring intently at Sean.
It wasn't just those green eyes he was looking at.
"Listen to me very carefully—"
Snape raised his wand.
"You have learned some trivial spells. They take many forms and possess varying degrees of magical power.
"I have trained you to deal with certain Dark Arts—how to prevent them, how to break them... but those are merely the weakest fraction of the Dark Arts.
"By all rights, illegal Dark Curses are far beyond what you should be exposed to. You cannot imagine, nor can you effectively resist, this brand of magic.
"And yet, a certain 'Greatest Wizard of the Age' actually believes you can handle them?
"The most foolish part is that there are idiots who actually believe they can face the most evil, darkest aspects of the magical world head-on—"
Snape's eyes were locked dead on Sean.
Sean was bewildered; he didn't know what Professor Snape had sensed this time.
Was it Ravenclaw's Diadem, the Gaunt Ring, or Slytherin's Locket?
As a double agent, Sean had never once doubted Professor Snape's aptitude for investigation and deduction.
"You know, Professor?" Sean asked.
"I know far more than you do..."
Snape gave a mocking laugh.
"Now, the sooner you understand what you are up against, the better. If you have never seen a thing before, how can you possibly hope to stand before it and..."
Snape fell into a sudden silence. He gazed at Sean, finally squeezing a word out through his gritted teeth:
"Survive..."
A few seconds passed before he continued.
"You'd best burn this into your memory, Green. Survival is the only thing that matters...
"If those people intend to cast an illegal curse on you, they will not announce their plans.
"You had better clearly and consciously realize this, you foolish boy. They won't be frank, fair, or polite when they curse you—you must be prepared. You must be vigilant.
"Now... Green, tell me. Which spells carry the severest penalties under Wizarding Law?"
"The Unforgivable Curses, Professor."
Sean was surprised. Was Professor Snape actually teaching him the Unforgivable Curses?
Why?
"You'd best know them. The Unforgivable Curses—the three most powerful, most evil Dark spells known to the magical world.
"They are the Killing Curse, the Cruciatus Curse, and the Imperius Curse.
"According to Ministry of Magic law, the use of any one of these three curses on a human being earns a life sentence in Azkaban.
"These three spells are classified together due to their deadly, cruel, and completely controlling evil nature. They are the signature tools most frequently used by them."
Snape paced back and forth, then suddenly picked up a slug.
"Imperio!"
The slug actually began to dance, though its movements were grotesque and disgusting.
"This is the Imperius Curse. It is now completely under my control. I can make it drown itself, I can make it jump out the window...
"Listen to me, Green. If you continue to be this stupid, I suppose this curse could be used on you as well. Lingering on in a wretched state is still better than being dead.
"Years ago, many wizards were controlled by the Imperius Curse just like this.
"That pack of fools at the Ministry, they can never distinguish who was forced to act and who acted of their own free will...
"However, the Imperius Curse can be resisted. I will teach you the method, but it requires immense strength of character. When you encounter it, you had best avoid being hit."
Snape finished speaking slowly.
Before Sean could digest the information, Snape continued.
"Crucio!"
Snape waved his wand at the slug. Sean could see the creature convulse violently. In moments, it couldn't even manage a wriggle.
"The Cruciatus Curse... exquisite torture."
"And the final spell. The Killing Curse, Avada Kedavra. When you hear these words, Green, run! Move those legs of yours. You'd best hide behind Dumbledore—Avada Kedavra!"
Snape spoke calmly, then chanted the incantation.
A blinding flash of green light pierced their eyes, accompanied by a rushing, chaotic sound, as if some invisible, massive entity were soaring through the air.
It was like the Grim Reaper swinging his scythe.
Simultaneously, the slug flipped over. It lay on its back on the table, bearing no physical wounds, yet it was undeniably dead.
"Unpleasant. And there is no counter-curse. There is no way to block it."
Snape stared into Sean's eyes.
"Dumbledore views you as the wizard he most needs to consider. He would not allow anyone to teach you such Dark Arts.
"As everyone knows, the Dark Arts corrode a wizard's mind, but..."
He looked at the young wizard before him.
He would rather nurture a Dark Lord than permit himself to be a failure once more, left with nothing but a corpse to collect.
"So... these three curses—the Killing Curse, the Imperius Curse, the Cruciatus Curse—are known as the Unforgivable Curses.
"Using any one of them on a human is enough to rot in an Azkaban cell for a lifetime.
"This is what you must resist. This is what I am teaching you to defend against. You need to be prepared. You need to be guarded.
"What are you waiting for? Take out your quill... write this down..."
Snape's voice mingled with the cold draft of the dungeon.
As Sean left the dungeon, somewhat bewildered but carrying the knowledge of the Unforgivable Curses, Snape remained in the shadows.
He extended his left arm. A brand was seared into the inner part of his left forearm, looking like a vivid red tattoo.
The sensation this Mark brought him had weakened by a few degrees again. The Dark Lord's power had been diminished more than once.
He didn't need to use his brain to know who this was related to.
But he would return eventually. No one could truly kill him; this had been verified multiple times.
And as for the person hindering his plans...
"Dumbledore—you had better have an explanation—"
Snape suddenly cast his gaze toward the dungeon entrance.
The old wizard with the long white beard was slowly materializing from behind the wooden door.