(I don't own Harry Potter or its characters, only this fanfiction's plot)

After snatching Gilderoy's wand from his loose fingers, Sirius yanked the pompous jerk up by the wrist. Gilderoy banged his knees on the roof tiles as he was dropped.

"Give me one good reason not to go to the aurors."

"You.." Gilderoy gasped as he struggled to his feet, panicked blue eyes trying to meet Sirius's, finding them unmoving as steel. "You must understand-"

"What I understand is that you're a liar and a con artist. A fraud who has apparently been brainwashing people so he can properly take credit for what they've done."

"Those people weren't cut out for fame, I was doing them a kindness really-" Gilderoy cut off at the look on Sirius's face. "People love my stories. My fans love me. I haven't even done anything wrong, really! Truly, the people I based my stories off of weren't going to do anything with their victories, so it's a win-win scenario."

"Keep telling yourself that," Sirius sneered. "You violated those witches and wizards rights to make yourself famous. Your fans, the people you lie to on a daily basis? They don't love you, they love the facade you put on."

"You're just jealous of me. Bitter that while I'll be remembered as fondly as Godric Gryffindor, all you'll ever be is a coward in our history books."

Sirius's jaw worked, before finally he turned on his heels.

Walking back towards the tower, the heir called over his shoulder, "I'll give you twenty-four hours to turn yourself in. Your sentence in Azkaban won't be as long then."

Sirius was already at the door by the time Gilderoy came to his senses. He hurried after Sirius like his arse was on fire.

It certainly felt that way.

"Wait!" Sirius turned around. "You don't want to get the aurors involved."

Sirius scowled. "Would you prefer I dealt with you myself?"

Gilderoy straightened, the same fake-smile on his face. "You wouldn't kill me. Not here, anyways. Too many people saw us together."

Sirius raised his eyebrows as he rolled Gilderoy's wand between his fingers. "You sure about that? Everyone knows I'm supposedly Voldemort's-' Gilderoy flinched at the name. "- big-bad second."

"Not a problem," Gilderoy said, recovering fairly quickly. "Not with what I know, anyways. Tell me, how did you figure out the animagi reversal spell wouldn't work on lycanthropes?"

"Because I have common sense? The rest of the horrifically inaccurate information just made it obvious."

Gilderoy, looking way too confident for a man who was wandless a hundred feet above the ground, laughed. "I see, and how were you planning to run the experiments? You have someone ready and willing I presume?"

Sirius's eyes narrowed. "What are you getting at, Lockhart?"

"Just that I've figured out your dirty little secret; you're a werewolf."

Sirius choked.

"A what?"

"How else would you know so much about lycanthropy? It's as you said, you'd know."

"Just because I'm not a fucking idiot doesn't mean I am one, you moron. Not everyone is as bloody ignorant as you."

"Aren't they?" Gilderoy folded his hands behind his back, smugly. "Even the Dark Force Defense League seemed more than impressed with my work, given their last letter inviting me to join."

Sirius opened his mouth to deny it, before snapping it closed. As ignorant as the average person was he shouldn't be surprised.

No one cared enough to understand lycanthropy, let alone study it.

"Thinking back, a lot of things make sense now that I think about it." Gilderoy started listing off things on his fingers. "How you were always missing during the full moon at school, looking exhausted the next day. The way you went ballistic if our teachers said anything against the furry creatures, the fact your own family never hosts anything on the full moon... Even the shine of the moon is in your eyes!"

"You're wrong," Sirius took a fortifying breath. "Just because I'm not an arse doesn't mean I'm a werewolf."

"Then how else would you know? There's no other explanation, unless..." Gilderoy tapped his chin in thought. "..Someone you know was one."

Sirius felt his blood run cold.

"Was it Potter? He was locked away for some time before his death, so it would make sense if he had been bitten recently. Or one of your other little friends?"

"What does it matter?" Sirius felt hot as his fingers clenched the unfamiliar word, sparks collecting at the tip. "Unlike brainwashing and fraud, being a werewolf isn't a crime."

Gilderoy smirked. Like he'd won.

"Yes, technically. But we both know it might as well be with how you'll be treated if this got out." Gilderoy shrugged. "I'm not an ungenerous man, so here's the deal; I'll keep your secret if you keep mine."

Ducking under his incoming wand, Gilderoy watched indignantly as his precious cherry wand clattered off of the roof. Down to the courtyard below.

It would take forever to find it.

Turning to glare at the man ruining his life, Gilderoy shouted, "Why the bloody hell did you do that?!"

Sirius shrugged, jaw clenching as he put an effort in to seem blase. "Sorry, must be my beastly nature showing through. Unfortunately for you, I don't play fetch."

"There's no reason to be so sore," Gilderoy replied, dusting himself off. "It's not as if you could understand my reasoning, anyways. Being born a Black guaranteed everyone would know your name, your stunt in and after the war even more so."

"Everyone fears my name." Sirius raised his voice. "They think I'm some kind of monster who killed his own family."

"Aren't you?" It took Gilderoy all of two seconds to realize this was the wrong thing to say.

"Big words from a literal mind-fucker." Sirius pulled out his own wand, taking satisfaction in the way Gilderoy's eyes widened. "Maybe I should show you how it feels, hm? Azkaban is obviously too good for a judgmental git like you."

Gilderoy said something- pleaded, but all Sirius could hear was the ringing anger in his ear. Telling him to hurt him, to kill him. A dark part of Sirius considered it, he would get away with it, after all. Gilderoy's wand history would support whatever testimony he made and Remus would never have to know how he nearly fucked him over.

This was the part of him that was like Walburga.

Smothering it, Sirius shoved his wand back in his holster.

"Ah! You scared me there." Gilderoy exclaimed, sweating. "I'll be more than willing to overlook this if you-"

"Go ahead."

Gilderoy blinked. "I beg your pardon."

Sirius met his eyes for the first time that night, unsure how he felt about the fear he sensed.

"I said," Sirius took a step forward. "Go ahead. Tell them I'm a werewolf for all I care, it won't change where you're going or who you are."

Gilderoy sputtered, but Sirius was done.

"And I wouldn't try to run, because next time? I won't be merciful."

He apparated away without further ado

Part 2 is out! Gilderoy is in deep shit now, and what will Sirius do if he goes through on his threat? There are only so many options without help, luckily he has plenty of that at his disposal

Though he may be unwilling to sacrifice the things needed for any of his family's plans to work, or more specifically the person.

I hope you enjoyed this :D Let me know what you think and like!