The classroom was so quiet you could hear the soft ticking of a student's pocket watch. Every pair of eyes was glued to the front of the room, where the collective breadcrumbs of their investigation were finally being baked into a terrifying reality.
"Wait a second," Cedric muttered, his voice cracking slightly as he connected the dots. "Professor, I need to check something. Harry's gift... the Parseltongue. It's not just a coincidence that he's the only one hearing voices, is it? The monster isn't just a beast; it's a creature of the serpent variety."
Sebastian leaned back against the edge of his desk, a look of genuine approval on his face. "Exactly, Mr. Diggory. The 'voices' Harry heard weren't ghosts or hallucinations. They were the predatory thoughts of a hunter. The reason the rest of you heard nothing but the wind is simply because your ears aren't tuned to that specific, ancient frequency."
Harry let out a breath he didn't know he was holding. "That's why it sounded like it was coming from inside the stones," he said, his voice rising with excitement. "It wasn't a ghost walking through walls. It was a massive snake slithering through the castle's secondary plumbing. The pipes are like a highway for it."
Cedric slammed his hand onto his desk, more in frustration with himself than anything else. "It's so obvious! Slytherin's mascot is a snake. He was a Parselmouth. If he was going to leave a 'legacy' to purge the school, of course it would be a serpent. How did we spend two weeks looking at magical lizards and spirits when the answer was staring at us from every green-and-silver banner in the Great Hall?"
The realization hit the rest of the class like a physical weight. The fear of the unknown was being replaced by the terror of the specific. Cedric, ever the diligent Hufflepuff, didn't just stop at the species. He pulled his copy of Fantastic Beasts and Where to Find Them from his bag and began flipping through the index with a frantic energy.
"Professor," Cedric said, his finger stopping on a page toward the back. "I think we're talking about a Basilisk. It's the only thing that fits the 'Acromantula's natural enemy' description. Spiders flee before it because they are its primary prey, and its gaze... well, the book says it's fatal."
"But wait," a younger student chimed in, "if the gaze is fatal, how is Filch's cat still breathing? And why is Justin Finch-Fletchley only frozen?"
"The water," Harry jumped in, his mind racing. "On Halloween, the floor was flooded because of the sinks. Mrs. Norris wasn't looking at the snake; she was looking at the reflection in the puddle. It's like looking at a solar eclipse through a piece of smoked glass. It dampens the effect. It doesn't kill you; it just... shocks the system into stone."
A slow, steady clapping sound filled the room. Sebastian was smiling, his eyes bright with the thrill of watching his students evolve into real investigators.
"Excellent deduction, Harry. Brilliant research, Cedric," Sebastian said. "The mystery that has haunted this school for a thousand years has just been dismantled by a group of students in a Muggle Studies classroom. The monster is indeed a Basilisk. A 'Class XXXXX' killer, the King of Serpents."
He raised his wand. "Since many of you have never seen one outside of a blurred sketch, let me show you what you're up against."
He pointed his wand at the heavy wooden lectern. The wood didn't just change shape; it seemed to groan under the pressure of a violent internal reorganization. The flat surface buckled and twisted, turning into a series of thick, muscular coils. The polished oak took on the texture of dark, iridescent scales, and the legs of the desk fused into a tapering, powerful tail.
The Transfiguration was so vivid that several students in the front row scrambled backward, nearly toppling their chairs. A giant, fifty-foot representation of a Basilisk now occupied the center of the room, its head brushing the rafters. Its eyes—huge, pale yellow orbs—glowed with an artificial but terrifying light.
"Don't panic," Sebastian's voice boomed over the whimpering of a few terrified third-years. "This is a construct. It has the weight and the scales, but it lacks the soul and the deadly gaze. Use this moment to understand the scale of the threat."
He walked alongside the massive wooden serpent, tapping its scales with his wand. "This particular beast has been alive since the days of the Founders. It has grown to its maximum potential. Its scales are as thick as dragon-hide, meaning most of your standard combat spells will simply bounce off like pebbles against a castle wall. Its fangs are filled with a venom that has no known cure other than Phoenix tears. And it moves through the dark, silent as a shadow."
The students stood in awe, touching the cold, wooden scales of the model. The reality of the 'adventure' had suddenly turned very, very serious.
"We cannot allow this thing to remain under our feet," Sebastian said, his tone turning cold. "But to kill it, we have to find it. Where is the door, class? Where does a thousand-year-old secret hide?"
"The Black Lake!" someone shouted. "Slytherin's common room is down there. It has to be deeper, under the water."
"No, the pipes!" another student countered. "We should just follow the loudest hissing!"
Sebastian waited, watching Harry. He knew the boy was close.
"It's the girl's bathroom," Harry said, his voice quiet but certain. "Myrtle died there fifty years ago. The writing was on the wall right outside the door this year. And that bathroom is always 'out of order.' Nobody goes in there. It's the perfect hiding spot."
Sebastian's smile widened. He gave a sharp wave of his wand, and the giant wooden snake collapsed back into a simple lectern with a loud clack.
"Theory is all well and good," Sebastian said, heading toward the door and gesturing for them to follow. "But in the Auror business, we prefer to confirm our suspicions with our own eyes. Leave your books. Bring your wands. We're going to have a talk with a ghost."