The final class of the day, Defense Against the Dark Arts with the Gryffindors, ended without Wilhelm drawing any attention to himself. Professor Quirrell or Voldemort was simply too busy staring at Harry and getting startled by his own reflection to care about what the students were doing.
Over the past few weeks, Wilhelm continued working on a perfect Rune Circuit. The one HelixTech had used in the future wasn't entirely his own creation, it had been developed by a group of several rune experts including Wilhelm working together. In truth, only about 3-5% of the circuit was his work. Remembering the full design was difficult, as even a small tile contained thousands, if not hundreds of thousands, of micro-runes layered beneath larger nodes.
Even though Wilhelm had managed to recreate some basic structures, the real challenge lay in stabilizing the layering. Micro-runes couldn't just be stacked randomly; each layer influenced the mana flow of the others. A minor error could cause the circuit to collapse or worse, explode violently.
So every night, after homework and dinner, Wilhelm locked himself inside his modified trunk, surrounded by parchment, ink, and blueprints of several machines. He practiced carving the tiniest runes by 'hand', testing various layering patterns on small tiles no bigger than a galleon because he didn't have the advance technology of the future.
It was slow, painful work. His fingers hurt from the delicate precision needed, and even with his future memories, progress was frustrating. Rune theory at Hogwarts was child's play compared to the rune circuit he needed to rebuild.
But Wilhelm didn't mind. He had time. For now, all he needed was a functioning prototype, a seed that could grow with him as he regained his strength and resources. After all as the saying goes 'Rome wasn't build in a day.' and neither was the future.
---
The Great Hall was buzzing with excitement, laughter, and chatter. Wilhelm sat at the Ravenclaw table, calmly eating roasted chicken and pumpkin pasties, when suddenly, the doors to the Hall slammed open with a loud bang.
Professor Quirrell stumbled in, looking pale and terrified. "T-Troll! In the dungeons!" he gasped. "Thought you ought to know..."
With that he fell unconscious.
For a moment there was silence. Then chaos erupted.
Prefects began shouting orders, and students scrambled to their feet trying to rush to the safety of their dorms in as soon as possible.
In the noise, Wilhelm heard someone whisper from nearby. "...Hermione! She's in the second-floor girls' bathroom! She doesn't know about the troll!".
Wilhelm's eyes widened. Without thinking, he rushed towards the doors of the Great Hall. Even if he had aged down, Wilhelm was still mentally and adult and seeing two kids rush to their death wasn't something he couldn't just let happen.
But the moment he crossed the door, a sharp pain ran through his chest.
He fell on his knees, clutching his ribs, gasping for breath.
Wilhelm looked down and froze in horror.
His fingers, they were fading, turning into dust before his eyes, then being blown away by an invisible wind.
Wilhelm panicked then but soon he understood what was happening.
'The timeline, Hermione's rescue. Harry and Ron are supposed to rescue her, it is an crucial event which shapes their friendship.' If he saved Hermione instead, that bond would never form. The butterfly effect would erase everything including him.
Gritting his teeth, Wilhelm forced himself to return back into the Great Hall. The pain in his chest slowly faded, his fingers became normal once more.
He leaned against the wall, breathing heavily, watching as Harry and Ron slipped out, unnoticed by the teachers.
'Some events are fixed,' Wilhelm thought grimly, clenching his fists. 'Interfere... and I'll vanish without even a memory left behind.'
---
Later that night, Wilhelm sat in his lab inside the trunk, the soft humming of the rune computer could be heard. The clicking of the keyboard could be heard through the silence.
Sitting on a stool, he leaned forward over his desk, fingers steepled under his chin. He finally spoke in a low voice.
"It seems," he said quietly, "that the magical dust from the time-turner embedded in my skin acts as an alarm... a failsafe."
He glanced at his hands, curling his fingers. They looked normal again, solid, steady not turing transparent or anything but the memory of them turning into dust was etched into his mind.
"If I take a step too far, if I change the fate of the world beyond certain limits, if I take the wrong choice... I feel it."
He pressed a hand against his chest, feeling the phantom pain lingering there.
"The pain starts in the chest... and then slowly, I start turning into dust, I begin to fade. Like a warning." He let out a shaky breath. "And if I ignore it... the moment I completely alter a major event... I'd disappear."
His voice dropped lower, almost a whisper.
"Not death. Complete Erasure."
He sat in silence as if still processing what had happened today.
"I walk on the edge of a knife," he muttered. "Too much interference, and I will cease to exist. Too little... and the world will collapse."
Wilhelm stood up and closed his eyes. "One wrong step and I'd be dust."
If he wanted to play hero he would have never travelled back in time in the first place. This wasn't some children's novel, it was reality and Wilhelm knew very well to treat it like one.
"I can guide. I can prepare. But I can't save anyone from their fate."
---
Disclaimer:
I do not own Harry Potter or any of the original elements from the books, movies, or universe. All rights belong to J.K. Rowling and the respective creators. This is just a fanfiction made for fun. I'm not a professional author—just someone who had an idea and wanted to write it down. Please don't expect perfect grammar or writing, I'm doing my best and learning as I go.