The first couple months of seventh year passed rather uneventfully for the Marauders; their classes gave them more work than ever before, preparing them for their N.E.W.T.s at the end of the year, but the four of them still found plenty of time to get themselves into trouble, particularly on the nights of the full moons.
Sirius's eighteenth birthday—the third of November—happened to fall the day before Slytherin's Quidditch match against Ravenclaw, so the Marauders decided to celebrate by redecorating the Slytherin common room with bronze-and-blue garlands and streamers, complete with a conjured screeching eagle. They returned to their dormitory just after midnight with a dog-shaped birthday cake they'd procured from the kitchen house-elves.
"Oh, this cake is delicious," Sirius declared, stuffing a large chunk of it into his mouth. "Tastes like Slytherin getting their arses kicked by Ravenclaw tomorrow."
"Especially if they're kept up all night by that eagle," James said with a grin. "I still think we should've added a lion head."
"Yeah, but that would've ruined the theme."
"I didn't know you were so concerned with aesthetics, Sirius," Remus said.
"Aesthetics are the most important part of any proper prank, Moony—you know that."
"A giant lion head wouldn't have ruined anything, Padfoot," James protested; "what kind of Gryffindor are you?"
"A Gryffindor who—"
"Reducto!" With a boom and a barrage of flying wood, a large hole was blasted through the Marauders' door just above the knob. A hand slipped through it and unlocked the door from inside, and a pack of Slytherins swarmed into the room: Snape, Mulciber, Avery, and a slender boy huddled behind them—Regulus. Sirius's heart clenched at the sight of him.
"What the hell?" James asked, standing up and dropping his cake. "How did you—?"
"You aren't the only ones who know how to break into other Houses' common rooms," Snape replied.
"I have no idea what you're talking about."
"Don't play dumb, Potter; we know it was you. We could hear Pettigrew's absurd little giggle all the way from our rooms." He glanced behind him. "Avery?"
"Incarcerous!" Avery swept his wand around to point at each of the Marauders—thick ropes shot through the air and wrapped themselves tightly around each of them, binding their arms to their chests and their feet together. James, who'd been standing, keeled over and landed flat on his face, having to wriggle and thrash like a worm to pull himself upright again. The Slytherins laughed; Sirius struggled against his ropes, desperate to get back at them, but they held stubbornly fast.
"What do you want with us?" Remus said levelly. "I'm sure you don't want to do anything that'll get you expelled from Hogwarts your final year."
"Oh, we're not planning on doing anything to you," Snape assured him. "We just came to remind you who we work for, and what will happen if you continue to mess with us."
"What, is Voldemort going to pop in and Avada Kedavra us for being mean to his precious new Death Eaters?" James's voice was filled with disgust. "You're pathetic, hiding behind someone like that so you can pretend to be braver than you actually are. No wonder Lily hates you."
"Estiflius!" Snape flicked his wand at James, and a thick wad of fabric pressed itself into James's mouth and gagged him. "I don't want to hear any more of your lecturing, Potter," Snape said through his teeth. "We're the ones doing the talking here." James grunted around his gag, his eyes glinting with fury.
"You should be careful how you treat us," Mulciber said. "Before long, the Dark Lord will be in control of all of Britain, and you'll be begging for us to show you mercy."
"You won't catch me begging for anything from a bunch of thickheaded blood purists," Sirius growled. "I'd much rather die."
"Blood traitor," Avery seethed. "You'd rather consort with Mudbloods and Muggles than your own people." He took a couple steps in Peter's direction; Peter whimpered softly. "And this one here's perfect proof of how Mudbloods are an embarrassment to our kind. Pettigrew can barely perform Lumos without one of you helping him out."
Peter drew up his trembling chin. "Well, if that's because I'm Muggle-born," he said quietly, "what's your excuse?"
Sirius let out a barking laugh, impressed. Avery's wand shot out again, and a moment later Peter had been gagged, too.
"We manage ourselves just fine," Snape growled. To demonstrate, he pointed to Sirius's half-eaten cake and summoned it into his arms without a word. "Looks like it's your brother's birthday today, Regulus," he said. "You didn't tell us—we would've brought presents."
"Regulus," Sirius said as his brother stepped forward for the first time. "Are these bigoted prats really the people you want to be mates with? Merlin, they're even worse than our parents."
Regulus pursed his lips. "You don't get to tell me who I can be mates with, Sirius. You abandoned our family."
"I didn't abandon you, Reg!" But Sirius knew that he had, in a way; he'd left his little brother all alone, no longer able to shield him from their parents' wrath. He'd left because he thought his brother had grown beyond saving. And looking at him now, his face full of hurt and anger and hatred, he knew with a sinking feeling that he'd been right. I'm sorry, Reg.
"We'll let you get back to celebrating now," Snape said. "Hopefully the ropes will have fallen off by morning." He glanced down at Sirius's cake. "Happy birthday, Black. If we catch you lurking around our common room again, it might just be your last."
Still holding the cake, Snape spun on his heels; the other Slytherins followed him from the room, snickering. Mulciber, the last of them, stopped in the doorway and glanced back at the Marauders with a sneer lifting his lips. "Morsmordre," he murmured, flicking his wand. Then he slipped out, pulling the damaged door shut behind him.
The Marauders stared blankly ahead at the giant symbol Mulciber had conjured, green and glittering like a constellation in the dim light of the room: a giant serpent slithering out the mouth of a hollow skull, fixing the four of them with its emerald gaze as it gave a silent, ominous hiss.
