Day 1
Regulus arrived at Potions class before Potter and his friends, which he considered a small win.
While the other students chatted and roamed around the room, inspecting the dark liquid that Slughorn must've placed in all the cauldrons before class, Regulus unpacked his bag, taking up as much space as he possibly could on the desk he and Potter shared. Let him suffer, he thought as he opened his potions textbook and began searching for whatever they'd be brewing today. The liquid inside his cauldron smelled vaguely of egg, though as for what type, Regulus hadn't the faintest idea.
He was flipping towards the back of the book when Potter, McKinnon, and Pettigrew appeared, quickly heading towards where Regulus stood.
"Beat me here, eh Reg?" Potter practically sang as he approached. He noted the considerable lack of space on their desk and just smirked, taking his place next to Regulus and letting his bag fall to the floor.
"You're just late," Regulus responded, coolly. Thankfully, that was the end of the conversation, as Slughorn entered the classroom and made his way towards the front, greeting students as he passed. Regulus took one last look at the page he was on before closing the book and staring forward, pointedly ignoring Potter, who Regulus could see watching him from the corner of his eye.
"Welcome, everyone!" Slughorn addressed the group with one of his anxious smiles. "Now, today we're going to begin with a review from last year...I hope you all remember how to brew Felix Felicis!"
The 7th years nodded and began murmuring excitedly amongst one another while Slughorn listed the potion's important properties. Though no one appeared to be listening. Regulus even heard McKinnon gush from behind him about how she'd mastered the potion before Lily Evans.
The potion didn't impress Regulus. He figured he'd need to drink an entire cauldron of the stuff before his luck turned around. Before a certain someone to his left stopped bothering him.
Potter's attention was fully on Regulus, who was now searching through his textbook once again to find the ingredients list.
"You haven't brewed this yet, right?"
Regulus scoffed at Potter's condescension as he flipped a page. "I don't need your help, if that's what you're implying."
"Well, since we're partners, we kind of-"
"I told you, we're not partners."
There was a second of silence as Regulus flipped another page, finally landing on the one that read "Felix Felicis", but before he could find the ingredients, the book was snatched out of his hands. He looked up, shocked to find Potter holding the book in his grasp, his eyes glittering with mischief.
"Give it back." Regulus shot the older boy an exasperated look.
"I know how to brew the potion. We don't need this," Potter tilted his head towards the book in his hand as he spoke. Regulus huffed and lunged forward, reaching out to grab the textbook and failing miserably.
"Reg, c'mon, we-"
"Don't call me that." Another unsuccessful attempt at grabbing the book followed Regulus' command.
Potter took a step backward, holding his free hand up in a motion that made him look as though he were taming a wild animal.
"Regulus, listen..." Potter started, slowly. "We're not going to survive this class if we're at each other's throats like this."
The younger boy crossed his arms and bit his tongue to keep from retorting.
"Just trust me!"
"I don't want to talk to you," Regulus unleashed, adding a teasing smirk.
Potter sighed, handing over the textbook. "Fine," he began as Regulus took it from him. "We don't need to talk to each other. But we're going to brew this potion together."
Regulus raised an eyebrow and set the book back on the table. "And how do you suppose we do that?"
It was silent again, the sounds of other students working and brewing filling the room, until Potter leaned down and reached into his bag. When he straightened, he was holding a sheet of parchment.
"Whatever you want to say...," he placed the parchment on the table between them, "...write it down."
Regulus nearly laughed before remembering he'd been the one who refused to communicate like a normal person. He didn't have the energy for fighting anymore and by now the two were well behind the other students, so he reached for his quill and grabbed the parchment, scribbling quickly.
Fine, the parchment now read.
Potter grinned in response and began writing the steps for brewing liquid luck down on the parchment, silently motioning for Regulus to retrieve the ingredients from the shelves on the other side of the room. The boy obeyed, but rolled his eyes as he walked away, wondering what he just got himself into.
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Somehow, the boys had managed to successfully brew Felix Felicis in complete silence, earning an approving nod from Slughorn as he passed by and examined the golden liquid.
As the professor moved on to McKinnon and Pettigrew's cauldron, Potter shot Regulus a smile and raised his hand for the other boy to high-five him. Regulus just scowled and looked away.
He was noting the slight changes Potter had made to the original Felix Felicis recipe in his textbook when he felt parchment scrape his arm. Regulus looked down, finding the piece of parchment the boys had been using to communicate, which was now covered in instructions, commands, and the occasional smiley-face from Potter, lying up against him. A new sentence was inked along the bottom:
I bet you wish I'd stay silent forever.
Regulus scoffed at the words and grabbed his own quill, adding below: It'd be nice.
A second later, Potter was writing a response and sliding it back over to Regulus.
Bet you dream about it. About my mouth, and the other things it can do...
His eyes widened and Regulus choked on a breath as he read what the other boy wrote. Potter laughed in return and motioned for Regulus to answer him. The younger boy's heart raced and his normally neat cursive turned slightly sloppy as he replied:
You arse, what the bloody hell are you talking about?
You're not denying it, was Potter's response.
Regulus shook his head and didn't bother coming up with a witty comeback. He dipped his quill back into the ink before writing: I'm gonna kill you.
Potter's laugh rang out again and Regulus hoped everyone was too busy with their own potions to notice. The older boy pushed his glasses up his nose as he wrote, the letters slightly slanted to the right when he shoved the parchment back over.
If you had to kill me, Reg, how would you do it?
A strange question to ask. But one Regulus had found himself wondering at least a hundred times before. He'd always found Potter annoying, and during his most obnoxious moments, Regulus found peace in imagining a Norwegian Ridgeback crashing into the castle and taking the boy in his mouth, or a black hole appearing and sucking away both Potter and his band of friends.
So, with Slughorn preoccupied by a group of struggling students towards the front of the room, Regulus took the parchment back and answered:
I've thought of about a hundred different ways I would go about it.
The response made Potter chuckle and pause for a moment, tapping the feather of his quill to his chin before he continued:
How macabre. That's one for every time I see you in this class.
Regulus glanced at the paper and hummed in agreement, his attention now on Slughorn who was back to the front of the room.
"Well done, everyone!" he announced to the class. "Now, in the remaining time we have, I'll explain what's due next week..."
Slughorn wasn't two seconds into describing their homework before the paper scraped against Regulus' arm again. He shot Potter an irritated look, but the older boy just motioned back down to the paper. There was a new sentence:
So, what's today's way?
Regulus inhaled, growing tired of this note writing by the second. He gave a one word response:
Freak.
Unsurprisingly, Potter just laughed and wrote back:
Do your worst, Reggie.
Regulus ignored the nickname and sighed, finding the one spot on the parchment that hadn't been covered in ink, and jotted down:
Day 1: Killing curse.
A second later, Slughorn dismissed the class.