The Disillusionment Charm would keep him from being seen; real combat ability would let him turn the tide if needed.
If Voldemort himself showed up to slaughter everyone, though, Sean would run a mile.
That said, the odds were tiny.
For that to happen, Dumbledore would have to let Voldemort slip the leash.
Mm… that's even less likely than Sean dueling Voldemort.
For such a result, Voldemort would first have to keep Dumbledore from noticing he'd slipped away—so the Headmaster wouldn't appear at once. Second, he'd need to find someone who didn't desire the Stone to touch it for him, since he himself couldn't handle it—and the Stone was the only reason he'd expose himself at all.
Truth be told, Philosopher's Stone reads less like Harry's coming-of-age adventure and more like Dumbledore's trap for Voldemort.
From the start, Dumbledore knew Albania was Voldemort's last hideout—and Professor Quirrell had just gone to "research" in Albania. When Quirrell returned, he wore that strange turban, and he hadn't been normal since. Dumbledore would not have missed this—why else send Professor Snape to keep an eye on him?
With Dumbledore holding the reins, Sean had far less to worry about.
Priority one: avoid Quirrell. Whatever the man used to be, he was undeniably dangerous now. No one knew what an unhinged Tom would do.
Second: keep track of the troll. For a first-year, those were the two real dangers.
And—equally important—don't expose himself. Keep the plotline on track.
Another morning.
The corridors rang with laughter; kids chased each other around. Worth noting, many of them carried thick, blue-covered notebooks.
Outside the stained glass, a giant kept hauling pumpkins across the lawn.
Hermione and Justin walked ahead, Neville trailing with his head down. Hermione sighed, "Neville, if you don't lift your head, that magic mirror is going to start shouting again…"
She always had a soft spot for him—especially after learning his parents had been long bedridden. In her eyes, this Gryffindor might as well have worn a tag that said, "Don't bully me, I've had it rough," which made her both annoyed and worried.
"By the way, Hermione—what do you think of that compendium?" Justin asked.
"It's… very good," Hermione said, raising the sky-blue notebook—only for the cutting draft to steal the rest. The corridor's wind was bone-deep; they couldn't wait to reach the Hope Nook and its roaring fire.
In a quiet corner, Justin cocked his head, eyes shining toward a shadow and whispered, "Sean?"
A small wizard's figure slowly resolved in the hallway.
Neville yelped; Hermione clapped a hand over her mouth.
"Mm. It's me," Sean said with a nod.
Looked like Hermione hadn't spotted him—mission accomplished. That was enough.
But then he looked at Justin, sighed—caught again.
"Oh, Sean, your Disillusionment's improved… but bring it on. This is the one thing I absolutely refuse to lose at!" Justin said, suddenly excited, as if a test had begun.
It was just like when Sean trained Finite: at first he couldn't cancel Justin's Beginner Levitation; later he could snap a Adept Levitation without breaking stride. The progress had left the room stunned.
Sean sighed again and rapped on the Transfiguration office door.
"Come in, child."
Professor McGonagall looked visibly busier by the day, as if trying to finish all the grading and prep for every lesson to come. Ever since Sean had started advanced Transfiguration, she hadn't stopped moving—yet no matter how busy, she always paused to watch him practice, correct his mistakes, and point him the right way. In that, Professor Snape was much the same—just far more impatient about it.
By the time Sean left the classroom, dusk was gathering.
In the corridor, he spotted Harry and Ron by the armor again, surrounded by a crowd of students.
"Sean's here!" Ron called. Every face—Gryffindor, Ravenclaw, Hufflepuff, Slytherin—turned to him, equal parts awe and gratitude.
…Slytherin?
Sean blinked at the small snake in a green-and-silver scarf beside Michael. That he didn't quite get.
"Today's the first release of the Green Compendium, Sean—we're here to thank you for generously sharing part of it!" Ron said, thrilled.
From the tremor in his voice, Sean pieced it together. Justin had quietly compiled a lot of his notes and, with Sean's blessing, published a first batch—for free. He'd meant to use the freebie to open up demand for other subjects, but then a variable dropped in—
Ron and Harry.
With their subject notes, they'd just piled up a bunch of points for Gryffindor, and before Justin could warm up his plan, it exploded. The notes were mobbed; Justin didn't even have a copy left for himself. Thankfully he'd only printed ten, and only up to the pre-Halloween material.
Still enough to give a lot of students a homework-free weekend.
Ron had marched the lucky recipients over to thank Sean, and at a moment like this even Slytherins in the line didn't ruffle him.
By the time Sean left the corridor, his arms were crammed with sweets. No wonder Justin had stuffed extra candy into his bag earlier—Sean almost didn't have enough to give back.
In the Transfiguration office—
"It would seem our Mr. Green is quite popular… wouldn't you say?" said a long-bearded, smiling old man, fingers steepled.
"Albus… aren't you perhaps taking a little too much interest in him lately?" Professor McGonagall's brows drew together, her tone turning grave.