SUMMARY: Severus feeds Regulus a Polyjuice potion, so that he may look like Severus's one big obsession... Regulus likes the prospects of finally getting to sleep with the one he loves, but is it really all what it's cracked up to be? One sided SSRB, one sided RLSS, insinuated RLSB (if you squint). Marauders Era. Regulus's POV. Contains slashy, underage sex, hee hee. HOTNESS!

A/N: I know... Worst title EVER, yeah? Sorry if there are any typos or grammatical errors - as usual, I can't be fucked to look it over one more time before posting it.

DISCLAIMER: I own nothing, and I don't earn money on doing this! All belongs to Joanne K. Rowling! Don't sue!

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"THE SUBSTITUTE"

"Get off!"

I stop hanging over his shoulder when he starts barking at me like an angry dog. I should know better than to hang over him when he's concentrating, but he's been working on this potion for months, and it bores me. I'm bored and aggravated – bored because…well, because it's boring, quite frankly, and aggravated because he pays more attention to this blasted potion than to me. It's not as though this is a school project, anyway.

Just yesterday he managed to get in a fight with my brother, and it all went ahead as he'd planned: Lupin tried breaking it up, and Severus lashed out at him, grabbing his hair and yanking out a few golden strands…

His determination is fascinating. Willingly getting into a fight with my brother and his friends (and getting a black eye out of it as well) just for a few strands of hair. Imagine that! They're not "just a few strands" to him, though… I know how intent he is on doing this potion. And I know that the way he looks at Lupin is not only with disgust. I believe Lupin thinks so – what else would he think? – but I know better. The way Severus talks about him… He talks very badly of Lupin, that he does, but just he talks so bloody often about him, it's quite obvious that he's not telling me the whole truth about his feelings toward the Gryffindor. He wants to possess Lupin, and that's why he's been brewing a Polyjuice potion. And what's more, he wants me to be the test bunny! I can hardly curb my frustration. See, I really wish he would want to have sex with me for the sake of having sex with me, in stead of it being a pathetic substitute for something that he can't have… But I've agreed to go along with this little project of his, just to be able to be near him. God help me.

He slips one hair into the cauldron – he doesn't want to use them all just yet. He needs to save some for later occasions, he explains to me. Only seconds later, the potion has just the right consistence and colour, and it's finally ready for consumption. After months of hard work, Severus Snape has succeeded in concocting the potion. He's clearly triumphant, but he doesn't smile – he smirks. I can tell he's getting aroused by the mere idea of feeding me this when we're finally alone up in his chambers.

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It was quite strange, you know, watching myself in the mirror after taking the potion… How I grew slightly taller, how I thinned, how my hair turned from pitch black to gold, how my nose grew longer and thinner, how my lips filled, how my eyes widened and turned golden brown, and how my skin paled. I couldn't believe this was me. What was even more sensational was seeing how Severus changed, too. He stood a few feet behind me, but I could still see him in the mirror – his dark stare, the way his now hard breath was making his chest heave, how his hands balled into fists… For the first time, I was genuinely frightened of him.

It wasn't hard for me to feign how Lupin might have reacted, had he been pressed up against the wall and sucked hard on the neck by a frantic, sexually predatory Severus, as I was currently being. I trembled with a mix of fear and anticipation – something I truly see Lupin doing, were he in my shoes. I started to say something, and once again I was amazed by the transformation. It sounded nothing like me! My silky voice had given way for the more raspy, but still gentle voice of Remus Lupin… The wonder subsided as Severus removed his lips from my throat. He'd started grinding against my leg, all the while whispering dirty words in my ear. The thing that put me off, though, wasn't really the grinding, nor was it the dirty talk: It was the way he called me "Remus". It felt strange, foreign… It was not until now it really dawned upon me how much he desired Lupin. Not me – Lupin. 'What's so alluring about that bloody bookworm anyway?' I jealously pondered while my shirt was being unbuttoned by eager hands, not realizing that my own crush was about as much of a bookworm as Lupin. I suspect that the affection Severus had for his so-called "enemy" lay in exactly that aspect… Or perhaps it was the fact that Lupin is a complete pushover – someone Severus could easily control, had he only been given the chance. Severus loves being on top, it seems.

Feeling hurt, I tried pushing Severus off me, only to find that the hold he had on me was hard as iron.

"No running away now, Remus…" he cooed. "Get on the bed."

As much as I wanted this, I couldn't help being a bit frightened. But I did as I was told, letting him yank my trousers off my bony hips – Lupin's bony hips, that is. I could tell that my being timid was arousing him… Although I wasn't even trying to act like Lupin, my behaviour was quite obviously just to Severus's liking. I was successful in behaving the way Lupin would – nervous, eyes turned downward, so bashful in my nakedness. Very Lupin-like indeed.

I wanted this. I wanted him to fuck me raw. The only downside was knowing that he wouldn't have given two shits about me, had it not been for the fact that I was looking like Lupin right now. I felt unappreciated, and started refusing his advances… I tried sitting up, tried covering myself, tried getting him off me.

"Don't!" he snapped, pointing a finger in my face, warningly.

"We haven't got much time anyway," he continued. "Lose the trousers. Quickly."

I did lose the trousers, and he started undressing as well. Soon, we were both naked, and I didn't dare to look at his erection. He grabbed my hand, and led it toward the very place I was trying to avoid looking. He moaned as he did so, and made my hand close around his rock hard cock… Despite myself, I was getting aroused as well. How I'd wanted to touch him like this!

He'd gotten between my legs now. I was still on my back, because he wanted to see my face – Lupin's face! – while he was fucking me. As he thrust into me over and over again, I thought I was going to die from sheer pleasure. He'd been very gentle in the beginning, but now he was buried so deep inside me, pounding into me with such force, I couldn't help myself from whimpering and arching my back, thrusting my hips back at him. He was amused, I could tell; he laughed lightly, called me a dirty slut, and so on… He was taking pleasure in humiliating me. I didn't mind, though; simply having his lips roaming over my body like that just felt so good… I started pumping my cock with the hand that wasn't busy being sucked on by Severus, and it didn't take long before I came all over my stomach. Severus liked seeing me – liked seeing Lupin – like this. He loved the moaning, the whimpering, and how my arse clenched around his cock as I climaxed. He didn't take long to come, either… And as he did, he moaned out his love for Lupin. I tried hard not to cry my eyes out.

Afterwards, he held me close in a spoon-position, and whispered how much he adored me – I mean, how much he adored him. Lupin. I'd be silly if I thought he was talking about me… Severus's kisses trailed from my left shoulder to the back of my neck, and when he got up to the hairline, I could hear him smelling the thick, golden hair. I could tell he was on cloud nine by the way he was acting, and I tried to play along, saying that I loved him back – which was true, of course, but I was hardly in the mood to say "I love you" to someone who'd only slept with me because I just happened to look like the one he loved. It seemed unfair, you know? How did Severus deserve having me, as a fake Lupin, tell him I loved him when he refused to tell me the same..? Severus wasn't talking to me… He was talking to his precious Gryffindor.

..I felt like dying.

It got even worse when I started to change back into myself, though. Severus saw that I no longer looked like Lupin, so he pushed me off him and told me to piss off to my room. He got up, and started dressing.

"Please, Severus… Can't we stay like this a while longer?" I pleaded with him, grabbing his arm to try and make him come back.

"No. Now, shove off." His heartlessness crushed me. Is this how you treat someone you've just had sex with?

"Please, just… I love you so much, can't you pretend I'm Lupin some more? Just for a few minutes..?"

Severus sighed.

"You don't understand a bloody thing, do you Regulus?"

"I understand that you love Lupin and not me," I said, all sullen now.

"Correct. Now that we have that cleared up, get the fuck out of my bed."

Reluctantly, I got out of the bed.

"…and the room."

Even more reluctantly, I left the room. Severus stopped me just as I was heading out the door.

"Don't tell anyone about this, yeah? Or I'll send a letter to your mum, explaining that you're a poufter."

The door was slammed in my face.

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I didn't care about Severus's threats – first and foremost because I wanted to muck it up for him, just for being such a heartless prick. Secondly, I couldn't care less what mum thought… Well, I did care, but I figured now that Sirius had run off and managed to get himself disowned in the process, my parents wouldn't want to disown another one of their only two sons, and end up with no heirs, no one to carry the honoured family name. See, they will do whatever it takes to keep the bloodline going... The fact that I'm a pouf is of course no obstacle for them in their quest to marry me off to some slag; that much I knew… I probably wouldn't refuse, either, seeing as I'd realized ages ago that trying to find true love was futile – the only one I ever loved was in love with someone else, so naturally I'd kind of given up on the whole business. I'll take whatever I can get, and whatever my parents coerce me into taking. So marrying me off would be easy, but if I'd been disowned there'd be no one to keep the bloodline going. And either way, if Severus threatened me any more, I'd simply threaten him back, saying that I'd send a letter to his father – who, I've heard, is a real bastard – saying that his son is a pouf. I would never do that to Severus, though… But the threat in itself is dangerous enough for him to reconsider the letter to my mum.

Anyway, I eventually told Lupin. You should have seen the look on his face when I told him about his hair in the Polyjuice potion, it was priceless! …After that, he's stayed out of Sirius and Potter's fights with Severus. And Sirius was of course all fire and brimstone, heh heh.

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THE END!