Archive of Our Own

Regulus Black knew what three quarters of the Marauders were doing, but only because he had seen them talking quietly among themselves when the fourth member wasn’t around. It was not new to him that Remus was a werewolf, it was at least obvious to him. However, being loyal to his brother and by extension his brother's friends, he would take the secret to his grave. Either way, he wanted part of it; mainly to help, and also because gaining that new skill would be extremely handy. Which is how he ended up surrounded by three-fourths of the Marauders staring at him.

" So, let's get this straight. Little Black wants to help and become an animagus with us?" a bemused James asked, turning to the older Black, who was grinning with a glint in his eye, while Peter looked rather hesitant. Regulus rolled his eyes at the use of the nickname before he looked at his brother.

"Reggie, Reggie," Sirius chuckled. "How proud I am of you. We would be honored to help you, my dear brother!” He finished with a playful bow and hand swish, causing tension Regulus didn’t know was there to leave his shoulders. 

Peter frowned slightly. “Wait, wait—we aren't going to talk about this?” he squeaked. “Have a vote?”

The question caused three different reactions: Regulus’ face went blank, although for those who knew him could see the wariness in his eyes; James’ eyebrows rose and almost disappeared into his fringe due to shock—whether at Peter’s unusual questioning or his audacity. Sirius’ reaction was perhaps more chilling, the way he stilled, eyes narrowed as he focused on the blond boy with a look that only those raised in a family like the Blacks could pull off, the look of someone who dares question the worthiness of a loved one. Since that was behind the question: could they trust Regulus, a Slytherin, with their plans to help Remus? 

“Tell us, Pettigrew,” a chillingly calm voice rang around them. “Why would we do that?” Sirius questioned, taking an almost predatory step forward to the already slightly cowering boy. 

“Sirius—I—” Peter stuttered, beady eyes avoiding making contact with intimidating silver eyes in fear it would cause an attack. Sirius stared at him, waiting for an answer, an excuse, anything. Nothing but stuttering and half-apologies were given.

“Next time, Peter, I would refrain from accusing my brother of being untrustworthy just because he is a Slytherin and a Black,” Sirius sneered before stepping back and turning to look at Regulus, checking to see if he is okay. After a suitable nod. James slid forward with a grin, only slightly strained from the dissipating tension.

“WELL,” he clapped, “since we have that out of the way, I think it is safe to say we should get started.” A mischievous grin appeared, reflected on Sirius’ face too. Peter, still recovering from Sirius’ display, nodded with a feeble smile. Regulus, choosing not to say or react to the display of brotherly protection, straightened up with a nod as a smile graced his lips, the mischievous energy dancing in his ice blue eyes. 

“Well, to the library it is.”

It took them till the start of fifth year—fourth for Regulus—to be confident enough to start doing the actual process. They needed to get mandrake leaves, which was fairly easy for the four with James’ invisibility cloak and Regulus putting his distraction techniques to good use. They had the four leaves with plenty of extras, just in case. Now, it was just the case of leaving the leaves in their mouth and not damaging them for a month. Regulus couldn’t help thinking it would be a better idea to have done this over the summer holidays but, alas they were not.

There was a good enough cover story for why they were not speaking. Peter acted as though he lost his voice while the Black brothers and James were attempting to have a competition on who can last longest without speaking out loud. Remus thought it was slightly odd but, if he was being honest with himself it wasn’t far-fetched for any of them and anyway, it was nice to have some peace and quiet.

While they were waiting for the month to be up, the next full moon, to be exact, they got to getting the ingredients needed for the potion and such. This was fairly easy since for the dew drops; all they had to do was get an area of in the Forbidden Forest that hadn’t been distrubed by or touched by sunlight.

Getting the phial that had received pure rays of moonlight and the chrysalis of a Death Head Hawk moth was going to be slightly trickier. Fortunately for them, Kreacher was a rather loyal elf to the Young Master Black. Regulus managed to easily convince Kreacher to discreetly buy the chrysalises and phials with a command and promise that Kreacher’s master and mistress wouldn't find out. 

It was finally the full moon and time to put the ingredients together. After placing the phials in areas, then having the Black brothers wipe the memories of Peter and James’ phials before wiping each others respectfully, all they had to do was keep meditating and chanting the incantation ‘Amato Animo Animato Animagus ’ while pointing their wand tip to their hearts. This would make it slightly difficult for the three Gryffindors sharing their dorm with Lupin and another fifth year student.

“I cannot imagine being in Gryffindor, sharing a dorm with four others?” Regulus teased. “I dread to think what it is like in there,” he finished with a shudder, however unable to conceal the gloating smile from the disgruntled three. Ah, the joys of Slytherin and having a family that could demand for their son to have his own dorm room, without anyone batting an eye.

After almost another month, they all started to feel a second heartbeat when they did their daily morning incarnation. Gestures and behaviors started to show themselves, or, at least, become more prominent, although no one noticed or could really tell. How could they? It was not like four underage students were becoming illegal animagi under everyone’s nose, no sane person would dare. 

Unsurprisingly, these four students were not sane.


A week after the full moon, dark clouds covered the sky like a blanket, a flash of light caused Regulus’ head to snap up before running to the window. He stared at the clouds, not breathing and heart pounding as the roaring rumble of thunder made his hairs stand on end—both in hopeful excitement and anticipation. There it was, the fork of lighting illuminating the clouds and with that cue, Regulus ran off sprinting to their pre-planned meeting spot in the forbidden forest.

Skidding across the grounds that were already becoming a dangerous skating ring of sludge due to the downpour that followed in Mother Nature’s fury, Regulus slipped into the edge of the forest, saving himself from a nasty fall by grabbing onto the trunk of a rowan tree, and straightening himself while taking a quick glance back to see if he was followed, which he was not, but that did not stop him getting tackled into the mud, eliciting a familiar barking laugh from his attacker.

“What the FUCK, Sirius?!” Regulus spluttered, his robes now splattered with mud, bits of twig and dead leaves stuck to him, as well as the streak of mud that covered the side of his face. 

“Aw, Reg, I thought you would be happy to see me,” Sirius grinned and looked down at his little brother, who was glaring at him while returning to his feet and trying to regain some dignity. 

“I am never glad to see you, dear brother,” Regulus bit back without any real heat behind his words. Sirius gasped in pain as he grabbed his heart, staring at Regulus in pain—he was even using the crocodile tears. The youngest Heir rolled his eyes but otherwise ignored his brother by heading towards the meeting place. 

However, Regulus was a Black and a Slytherin, he wasn’t going to let that trick go without consequence—it was not in his nature. 

“Oh, brother, how you wound me!” Sirius, sobbed dramatically. “Does my—” 

A sudden shriek and well-sounded splat cut Sirius off from his speech. Turning to look over his shoulder, Regulus was delighted to see Sirius was pushing himself up after faceplanting into the mud—totally not caused by a well-placed tripping jinx. The comically dangerous look on Sirius’ face said everything. Regulus started sprinting, his cackling following him, almost drowned out by the drums of thunder and pouring rain.

“Get here you, LITTLE SHIT!” Sirius growled, chasing after him.

After dodging the trees and avoiding the odd trip jinx thrown at him, he burst through a familiar patch of ferns and almost barreled into Peter. James jumped in surprise, managing to catch them both and keep his balance. 

“Thank you,” Regulus said as he righted himself. “Sorry for being late, I had an issue.” 

Following this was the familiar muttered cursing and the sound of running feet sprinting out from the ferns, skidding across the ground and hitting Peter like a bowling ball. It really was not Peter’s day. Poor Peter Pettigrew.

“They TRIPPED me into the mud” Sirius exclaimed, pointing accusingly at a not so subtly smug Regulus. “Now look at me, my hair! My face!” James was trying to keep a straight face while he helped Peter to his feet, who looked Sirius dead in the eye.

“I think it is a major improvement,” he deadpanned. Regulus and James both erupted into roaring fits of laughter while Sirius’ jaw dropped. He crossed his arms as he straightened up while James, who was still giggling, threw an arm over Sirius’ shoulders. “Ah, my dear friend, did you know mud is good for the skin?” James said teasingly, poking a finger to the less covered cheek.

“Is that so?” Sirius rounded on him before he could react, tackling them both into grass. The other two both watched on, amused and exasperated at their antics. 

After a few minutes they stopped. Sirius sat up and looked at James then Peter. 

“So, do you have them?” he asked. 

Peter nodded, rummaging through his bag and pulled out four labeled vials filled with a red liquid. They each took their respective phial and all looked at each other as a nervous energy sparked between them, creating an almost on-edge tension.

“Count of three?” Regulus suggested. 

They all nodded.

“Okay then,” James started. “One, two…three!” 

They all simultaneously knocked back their potion in one gulp, faces pulled that let others know the taste of their own was no better. Then, the familiar ritual chanting they have been doing every morning began.

Regulus, eyes closed, repeating the chant, started to see a small figure from far away. The longer he concentrated and chanted, the closer the figure came, until it was the obvious outline of a cat, causing his breath to hitch when he suddenly felt a burning sensation take over his body. That’s when the painful ache ripped through him as he felt his bones compress like he had just been stood on by a giant, with the uncomfortable sensation of his collarbone melting. Somewhere in the back of his mind, he registered that his face was in the grass and heard other grunts and cries of pain. A violent itch, accompanied by the feeling of being stung by wasps scattered over his body, while the uncomfortable sensation of his ears melting into the side of his head and traveling upwards.

The uncomfortable, painful sensation of his body transforming into something smaller and completely different lasted for what seemed like ages, when really it all happened in a space of fifteen minutes. Once he opened his again, everything was different. Where there were vibrant greens and such, there was now an obvious dullness to the colors he saw in his new form than that of his normal one. He shakily pushed himself up from laying on the ground. Having four paws was an odd sensation yet felt oddly right. He slowly looked around himself to see that he was a semi-longhaired black cat. Ears twitching at the noises, he looked over at the other three to see a tall stag, a big black dog and a brown rat. He focused on the rat, longer than he wanted to—the primal, animalistic side of his brain recognizing that it was prey.

The rat turned, and froze, sensing its prey before scappering up the legs of the deer. Regulus blinked as he realized he was getting ready to pounce. Sitting back and looking at the fellow animagi, it did not take long for him to work out who is who. James, of course, had to be the stag, while the rat was Peter and, to Regulus’ amusement, Sirius Black was the shaggy, black dog.

Speaking of the dog, he started barking…at Regulus…oh no. 

Instinctively, Regulus arched, with fur standing on ending and puffing up, letting out a hiss in warning at the shaggy mutt as it barked and wagged its tail. Obviously, to Regulus’ annoyance, Sirius ignored the warning, and ran for him, causing Regulus to spin and dart off around the clearing with a dog at his tail—literally, as canine jaws snapped at him just before darting up into the safety of the tree.

After a few barks, Sirius turned back and looked up at the glaring cat above him with the signature troublemaker grin.

“My little brother is such a sweet kitty,” he teased, the uncanny ice blue eyes of his brother glaring daggers into him. James skipped over, swinging an arm over Sirius and flashing Regulus a grin as well, with Peter shuffling behind who was eyeing Regulus warily. Regulus rolled his eyes. 

“Psh psh psh, come here little kitty,” James sniggered at the unamused look he was given, while Sirius laughed. Regulus, thinking he might as well get it over with, stood up on the branch and looked down. Steadying himself and hoping to Merlin his judgment was right—he jumped down off the branch to the trunk and ran down, before coming to a less than elegant stop at Sirius’ feet, who took a step back along with James to give him space to transform back to himself. Which, he did by seeing himself in his mind’s eye and focusing on that.

He stood up and brushed himself off, casually, before smacking his brother. Sirius, expecting this, laughed it off before trapping his younger brother into a headlock. “Always knew you were a stuck up cat.”

“Better than being a filthy mutt.”

“Me? Filthy? ” Sirius, gasped. “I am not FILTHY! ”

“You’re a Gryffindor.” Regulus replied, matter of factly, as he wiggled his way out of the headlock while a chorus of “HEY!” followed by the three Gryffindors. A Slytherin hanging around with three Gryffindors. What had come to this world?

“Anyway, you may jest at my animagus form but, at least my isn’t like Sirius Black the Black Dog, ” Regulus grinned at his brother while they started to slowly make their way back to the castle. Sirius sniffed, tilting his head up giving the illusion he was looking down at everyone.

“Yeah, well if I remember correctly,” Sirius smirked, “the star Regulus is at the heart of Leo . A Gryffindor at heart.” 

An offended hiss sounded from the youngest’s lips. “Yes, well I am a cat, but I assure you that I have self preservation and I am not a reckless idiot,” Regulus sniffed in annoyance. James rolled his eyes at the two brothers.

“How are we going to tell Remus?” Peter asked, catching up. They all looked at each other before James spun around, making a grand open gesture with his arms.

“We just show him!” he exclaimed, making jazz hands. The rest stopped and stared at each other before shrugging and agreeing.

“Where though?” Regulus asked.

“Our dorms, duh!” Sirius replied, rolling his eyes.


That is how Remus walked into a stag with its antlers stuck in the curtains, a cat clinging to the bed frame, a dog barking at the cat while leaping around, all while there was a rat on his bed.  

The coming years were going to be interesting, to say the least.