7th-year Potions is sort of a joke, and Tony doesn't mean just the material - there are useless lumps like Reed Richards in there and he wouldn't know Wormroot from worm food. But it gives him the chance to throw stuff in a cauldron and force himself to make it work in some way, and his exercises are more challenging than the silly work-throughs the book has.
Slughorn is on another "house cooperation" kick, which means after the first week they get assigned class partners from the other house - Slytherin shares the block with Ravenclaw - and Tony ends up paired with this dorky-looking guy with wire-rim glasses who introduces himself as Bruce. Tony is all set up to fake a particularly nasty illness that requires him to miss just Potions and make it back in time for Quidditch practice when Slughorn hands out their assignment for the next three weeks and it actually looks fun.
Design a potion that has at least three practical applications that does not already exist in a simpler form.
"The winning pair," Slughorn says, as he rounds the tables with his hands behind his back, pudgy face flushed, "will receive a rather special item from my personal storeroom as congratulations for coming out at the top of the class."
"Does this mean we can take a complex potion and make a better, simpler one?" Bruce asks aloud, as the room explodes into hushed whispers and animated hand gestures.
"Or that we can take two existing ideas and combine them into a single application?" Tony suggests.
Tony stares at the parchment on the table between them. "Or, maybe, we could take an idea that exists in magical form some other way, like a charm, and-"
"-turn it into something you can ingest and use as a potion?" Bruce finishes.
There is a long moment where they simply stare at each other.
"Okay," Tony says, "this term might not suck so bad after all."
The initial idea requires a lot of extracurricular reading in the library, which is apparently Bruce's second home or something. Tony finds him the next day, after the last class, buried in a small mountain of books that he's going to get in so much trouble for if he doesn't re-shelve them correctly.
"I think you need to get out more," Tony tells him, seriously, and sits down across from Bruce with his back to the stacks.
Bruce just sort of ignores him, which is new. "I think a lot of people are choosing simple things, like small inanimate to animate transfigurations, but I think we should go big."
"Go big or go home," Tony agrees. He nods. "I like it. I was thinking flight."
"Flight?" Bruce blinks at him.
"You know, like charming something to float. Broomsticks. Look, it'd be awesome to be able to fly around without having to be on the pitch is all I'm saying."
The other boy stares at Tony for a long moment, and sets down the book in his lap. He takes off his glasses, pinching the bridge of his nose a bit - it looks more like a thoughtful tic than restrained annoyance. "It might be possible."
"I don't operate in 'mights'."
"If we stabilized the charm somehow to keep it localized to the liquid itself and then to the person who drinks it," Bruce starts.
"And somehow give control to the wielder," Tony adds. "Otherwise..." He smacks his hands together. "Kapow. Game over."
Bruce looks excited now. He digs around in his monster pile of books for some old tome that's pretty much falling apart. Pages actually flutter out when he goes through it.
"So, we'd need to work in a lot of give to the original compound in order to allow for adjustments during the flight itself," he says.
"My usual method is just throwing stuff together to see what happens," Tony admits. "This may require some additional calculating."
"We can meet here and work through the formula," Bruce offers.
Tony is half-aware that he's already well on his way to forgetting he is taking any other classes that may or may not have assigned a three-foot essay on Goblin revolutions due next week. "Okay. Let's re-convene tomorrow with our initial thoughts and see what we are starting with."
"Deal," Bruce says. He looks happy - alive, if Tony had to put a word to it, and Tony knows the feeling intimately. Tony is going to go back to his room in the dungeons and probably forget to sleep tonight.
On his way out, he thinks he sees somebody skulking around the edges of the section, but it could have been just a trick of the light - it is rather dark in there.
Potions the next day consists wholly of Tony and Bruce bent over their shared table, scribbling out ideas and formulaic hypotheses onto spare parchment. By the end of the class, they've ruled out at least six compounds that they deemed too unstable, four that included ingredients too dangerous to combine together, and one that Tony was curious about but Slughorn had 'tsk'-ed at as he walked by (so it went in the rejected pile).
Tony is feeling very good about their latest attempt, a scrawl covering a foot of parchment with notes and scribbles from both their hands, when a shadow slinks over the area where he is scratching out the current thought in his head.
"Stark," says a nasally voice.
"Riddle," Tony replies, without looking up.
"What do you think the prize is for the winning team?" Tom Riddle asks. He leans over the table and onto the parchment, his elbow in the space that Tony needs to finish his re-calculation. Tony frowns and pokes at the offending appendage until it moves back a bit. "Liquid luck? Molten gold? Something better?"
"Hopefully something to repel you and make you go away," Tony tells him.
Tom's mouth twists down into a scowl. "You think you're clever."
"We could market it and make a fortune," Tony continues, and jabs the other man with his quill. "And I know I'm clever, there's a difference."
"You're infuriating," Tom says.
"And you need to shower," Tony replies. He shoos the man with his empty hand. "Go back to your pissing contest with Richards, smart people are working here."
He gets an expression contorted in rage in response, but at least Tom pushes himself back away from the table and returns to his own. On Tony's left, Bruce snorts a bit. "Nice guy."
"He's a dick," Tony says. "Gives me the creeps."
"And here I thought you guys were best friends," Bruce laughs.
After a week, they've got a working base compound that Tony thinks is stable enough to take the adjusted formula and the volatile ingredients he's hoping will combine without much of a fuss. The other pairs in the class are achieving varying degrees of success with their own creations - one pair has already blown up three cauldrons, much to Slughorn's chagrin, but a few others seem to have something going that seems relatively successful, though Tony assumes they are all doing the simplest potion they could come up with.
Tom keeps trying to come over by Bruce and Tony's table, obviously jealous, and Tony has half a mind to start shocking him with a spell every time he loiters too close for too long.
"I think we need to get some outside input on the mechanics of the floating charm," Bruce says, staring down at the bubbling cauldron like he's afraid the whole thing is going to blow - it won't, Tony double-checked all the formulas.
"What do you mean, outside input?" Tony asks.
"Charms aren't really my strong point," Bruce admits. "I just think maybe we should get the opinion of someone who really knows them."
Tony glances over at Tom and Richards, who are arguing over something as their cauldron wobbles dangerously on the table. "Absolutely not."
"Not him," Bruce replies. "Just meet me after class is over today out near the greenhouses, okay?"
Truth be told, Tony isn't really sure what to expect when he finds Bruce sitting near a cluster of trees that sort of lead into the Forbidden Forest, but it certainly isn't that they stop at the foot of one of the larger ones and look up into the branches.
"Clint!" Bruce calls.
"What's a Clint?" Tony asks.
Instead of an answer, Tony gets a quill shooting out of the leaves and narrowly missing his cheek. He hears the contact behind him; when he turns, he finds it embedded into the trunk of another tree, through the heart of what appears to be a makeshift target made of colored rings of paint on a piece of parchment.
"Huh," he says, impressed against his better judgment.
A guy hops down from the branch he was apparently nesting on, dressed in Hufflepuff uniform. "What's he doing here?" he asks Bruce, eyeing Tony warily.
"We're partners in Potions," Bruce explains. "Listen, we need your help with Charms."
One half of Clint's mouth quirks upwards. "You failing Charms, Bruce? And here I thought you were so smart."
"Uh, no," Bruce replies.
"Are you charming these quills?" Tony asks, because now he's curious. He leans in to the target to see that the only holes in the parchment are in the bull’s eye - that's really something. "And using them like arrows?"
Clint shrugs. "Wouldn't let me bring my bow in."
"Oh, I like this guy," Tony tells Bruce. "How do you even know him?"
"Tutored him in Transfiguration," Bruce says, and shrugs.
"So you need my help," Clint says. He seems smugly pleased by this. "Fine. Help me with my History of Magic essay, and it's a deal." He pauses for a moment, tilting his head to one side, and adds, "Also, you know some oily guy from Slytherin has been following you since you left the greenhouses, right?"
Tony groans. "Son of a - Tom."
Clint, as it turns out, is sort of a Charms prodigy.
"What you'll need to do is mimic the magic of it," he says, floating Bruce's books up in the air and weaving them between one another. "Since there's a large element of control there, I'm not sure how you'll want to work that in."
"Maybe if we kept it open, like the spell does," Bruce mumbles, scribbling furiously onto his notes. His hands are covered in ink, and when he pushes his glasses up his nose, he gets a streak of it across the bridge. It's kind of cute, in a nerdy, dorky sort of way.
Tony runs a hand through his hair. "We could probably do that. We could factor that out of the equation-"
"-and instead leave it open, eliminating the need to calculate it," Bruce says. "Besides, we won't know specifics of how much the person weighs or how tall they are when putting it together."
"We could use a stable ingredient as a blank variable," Tony adds.
"And add in something like Ptolemy to bind that to the person who drinks it."
"So that we don't have to calculate out specifics," Tony says.
Bruce grins, wide and white. "And it will automatically be factored in after it's drunk."
There's a long moment of silence, when Tony and Bruce just stare at each other, overcome by knowledge, and then Clint clears his throat and says, "I have no idea what you just said."
It's late, so they break for the night, and Tony is itching to go work on the formula again with their new additions, even though he knows they can't go back down to the Potions classroom again until class tomorrow.
"By the way," Clint says, as he gathers up his quill-arrows and stuffs them in his bag, "that guy who was following you? Has been loitering near the girl's bathroom on the second floor a lot lately. Kinda weird, if you ask me."
"He's always weird," Tony scoffs. Then he sobers a bit. "Wait, which bathroom?"
"Second floor," Clint repeats. "He's gone in a few times and hasn't come out for hours. Seeya round."
After he's gone, Bruce turns to Tony with a frown. "What do you think Tom's doing in there?"
"Practicing his curtsy in the mirror? I don't know," Tony says. He shrugs, thinking about their potion. "Tomorrow, let's get this added to the mixture - I think it's going to need some time once bottled, because if we go by the cooling principle to Mercury, it's going to need to be removed from air to do so."
They bottle the potion into two small vials - one for each of them to try - and Bruce gives them to Tony to keep in his room ("Because the dungeons are a lot cooler, just make sure you keep them somewhere safe."). Then Bruce disappears for a few days and Tony is busy with Quidditch practice - after all, the Gryffindor/Slytherin match is coming up and if Tony doesn't knock at least two people off their brooms, he'll be disappointed in himself - and he thinks only idly about their chances of winning Slughorn's prize.
Tony meets up with his partner again in the library, at one of the big tables near the windows.
"You've been quiet recently," he says, as he sits down.
"Did you know there is a labyrinth of tunnels supposedly built into this castle?" Bruce asks. He's nose-deep in a book that is about half the size of the tabletop itself.
Tony peers in - the book doesn't look like something that would normally be shelved near Hogwarts: A History. "The hell are you talking about? How do you know that?"
"It's in this account of Rowena Ravenclaw I got from the Restricted Section."
"How did you get in to the Restricted Section?" Tony asks.
Bruce just peers at him through the lenses of his glasses. "I've got a term-pass."
"Of course you do," Tony sighs. "I don't know why I even asked that question. But what's this about secret tunnels?"
"Tony, do you think-" Bruce cuts himself short and leans forward across the table, eyes wide and cheeks flushed. "Do you think Tom found the tunnels? Do you think that's what he's doing near the girl's bathroom?"
"Well, it's certainly less creepy than the alternative suggestion of what he's doing in there," Tony says.
There's a long moment of silence, and then Tony says, "Let's go see what he's up to."
"What?" Bruce starts.
"The potion'll be ready tomorrow, and we've got to try it before we turn it in, even though I'm sure it's correct," Tony points out. "So, let's try the potion and go flying through the secret tunnels and figure out what Dick McDickerson is up to."
Bruce shuts the book with a snap and a cloud of dust. "He's got to be doing something, right?"
"He's always going on about things," Tony sighs. "'Blah blah, Muggle-born, blah blah pureblood,' it's really rather annoying."
Bruce gives him a very small, sheepish smile. "I'm Muggle-born."
"And I give zero shits," Tony says, and stands up so he can pat Bruce on the shoulder as he reaches for some of the books to help put them away. "You're the best Potions partner I've ever had."
They put the rest of Bruce's books back on the shelves in silence.
"Tomorrow, just after curfew," Tony says, once they are done. "Meet me by the second floor girl's bathroom - there's got to be something there."
Bruce nods. "Alright."
When Tony gets back to his room, he checks on the potions. The hair on his arms is standing up for reasons he can't figure out - he's pretty sure he left the bottles beneath his bed, in his trunk. Nothing seems to be broken or missing, but when he pulls them out, he doesn't think they are exactly in the same place that he left them. He peers closer - is one of them a slightly different color, or is that a trick of the light? He doesn't think anything they added should have given the liquid a greenish tint.
Tired, he slips them back into the trunk and sleeps.
"Ready?" Tony asks, standing in the girl's bathroom the next day, when the castle is very dark and he stubbed his toe twice getting around without giving himself away.
Bruce nods. "Ready."
Excited by the prospect of flying without a broomstick - and of potentially finding out that Tom is doing something that could get him kicked out of school - Tony pops the stopper off his vial and drinks it. For a long second, he can't feel anything at all. Then, his legs start to tingle.
Letting out an excited whoop, Tony concentrates on the sensation and pushes, for lack of a better term, into the air - his feet leave the floor and then he's flying, a little off-balance and unable to get a straight line, but he's flying, and it's the best feeling he's ever had - the still air of the sleeping castle cool against his face.
He glances down and over at Bruce, hoping that the other boy will be into a game of air-tag in the corridors, but Bruce is hunched over on himself, hands covering his face. When he steers himself closer, Tony can see that the boy is trembling.
"Bruce?" he asks, joy vanishing. "Bruce, are you-"
Bruce lets out a roar; a real roar, like the kind that monsters in the Forbidden Forest make, and Tony tries to stumble back before he realizes that his feet aren't on the ground. He ends up sort of tumbling against the far wall.
Bruce is turning green. He's also doubling in size, uniform shirt ripping as he's two, three, well over four times his normal size. He's all muscle, color a cross between some horrible monster from a legend and the walls of Slytherin's common room walls. He roars again, arms stretched wide, and he looks... mad.
"Oh, shit," is all Tony gets out before Bruce is lunging at him. He can't move fast enough with his floating form. Bruce's bulk hits him hard, sending him flying back into the wall; he hits his head and loses control of the charmed-properties of the potion, slumping down to the ground in a heap, feeling dazed and dizzy and very confused. He hears another roar above him, and then a horrible crunching of stone and rock, and by the time he pushes himself up onto all fours, Bruce has disappeared into the bathroom and there is water spraying out the doorway from where he's apparently dismantled a sink.
"Bruce!" Tony cries. He shakily gets to his feet and concentrates on the tingle in his legs again - the potion seems to be lasting awhile, at least, and he wishes he had more time to spend on congratulating himself on formulas well-done. But Bruce has disappeared inside the bathroom, and all Tony can hear is a roar - distant, like Bruce is much further than just in one of the stalls.
Tony flies into the bathroom. The sink - or what he assumes used to be a sink - is gone from the middle of the floor; instead, there is a huge, gaping hole, far deeper than simple pipes should be. Tony grabs for his wand and looks down it. Somewhere within, he hears Bruce roar in anger again. They've found the tunnels, it seems - and Tony doesn't have much of a choice but to follow his friend down.
"Okay, big guy," Tony says, mostly to himself. "I'm coming after you."
The tunnels are long and kind of damp and Tony can't totally see where he's going, which is concerning, since flying is a bit faster than running would be and he's afraid he's going to smack into something. He passes what appears to have been some kind of password-locked door - ornate and decorated and now very, very broken, so he hopes it wasn't worth all that much. He hears Bruce roar, and it sounds closer, so he keeps going.
He finds the other boy standing in a huge open atrium, with water on the sides and at least sixteen statues of snakes lining the middle path. Bruce is standing, green and huge and wet enough that the dim light is reflecting from his skin. He turns when Tony manages to set himself back down on the ground, hands out in front of him.
"Hey, hey," Tony says, hoping he sounds soothing. "Bruce, it's me. Tony. Remember me?"
Green-Bruce growls and starts forward a bit.
"Whoa!" Tony cries. He hops back a step. "Tony! Friend Tony! We made a potion together, remember? Now, I'm pretty sure somebody tampered with it, and I think it was Tom-"
He is cut off by a furious roar.
"Yes! Yes, exactly, Tom is an asshole. He's a grimy, nasty asshole and as soon as we get out of here, I'm going to find him and do something particularly painful to the protruding parts of his body."
Green-Bruce's eyebrows are furrowed, but he looks less sure. He growls again, and Tony might actually be getting the hang of figuring out what he's trying to convey.
"I'm your friend," he says, again, and risks taking a step forward. "I'm Bruce's friend, and I'm your friend."
There's a moment, and Green-Bruce snorts in a way that almost might be a laugh.
"Sure, I'm your friend, too," Tony chuckles - it's a bit forced, but maybe Bruce won't really notice. "You know, normally, Bruce is pretty... small. Kind of shy, I guess. Sits all hunched over like he hopes nobody is going to notice him. It's a bit cute, I guess. He's sharp as a tack, and he hopes nobody notices."
He's calming Bruce down, at least, and that's something. Tony keeps moving forward, trying to take in as much of their odd surroundings as he can while still not getting pummeled by fifteen-feet of scary green muscles. "Listen," he starts, "we're going to get out of this, and we're going to-"
There's a very loud hiss from somewhere behind them both. Tony stops, glancing around Green-Bruce's suddenly tense and growling form, to see a giant snake slither out of a stone statue.
"For fuck's sake," he gasps. "What is that?"
Green-Bruce roars and takes off towards the snake, and Tony launches himself into the air. Maybe he can stay high enough to be out of range - and he's not sure if anything can even hurt Bruce while he's in giant green rage monster mode, but he's a little concerned anyway. He aims his wand and gets a good hit of Expelliarmus in, enough to send the snake flying backwards against the far wall. Bruce follows, bellowing in anger.
"Bruce!" Tony shouts, flying in closer. The walls are starting to shake with the force of Bruce's fists. Whatever Tom did to the potion, it's insane. The guy's got more strength than an army of Manticore. Tony is afraid the whole thing is going to come down around them, and he doesn't plan on letting that happen.
He circles around, watching Bruce roar and reach for the snake's neck, wrapping huge green hands around where the creature's neck might be. Bruce slams the snake down against the ground, and Tony hears something snap, and then the walls really start shaking and he knows they have to get out or else risk getting trapped.
"Bruce, we gotta go!" Tony cries. Green-Bruce looks up at him, and there's something there - something of real Bruce, at least, and Tony is going to hold onto it. He soars towards the hole that used to be a door, leading back up to the bathroom. "Follow me!"
He isn't sure how he's going to get something that big out, but he needn't have worried; as he flies up the hole in the pipes, Bruce follows, leaping from side to side and digging massively powerful hands into the rock until they are back in the flooding bathroom and Tony collapses on the floor, weary and terrified and exhilarated all at the same time.
He's soaking wet when Bruce shrinks back to his normal size, completely naked and lying on the tiles. He looks very confused when he lifts his head up.
"Hey, buddy," Tony says, and manages a weak smile.
"What the hell just happened?" Bruce asks.
That's when Dumbledore and Slughorn race in, wands at the ready, and Tony just hopes they aren't going to get expelled.
The whole thing is, as it turns out, called an unfortunate accident, including the part about the collapsing secret tunnels and hidden giant snake (Basilisk, Tony learns) and the bit where Tom Riddle has gone missing and they think he was probably hiding in the tunnels when they all fell down on him.
"Gee," Tony says, trying to summon false sympathy while sitting at the Slytherin table in the Great Hall, listening to the Headmaster's speech, "I'm just so torn up about Tom. He was such a great guy and all."
He cranes his head around to find Bruce at the Ravenclaw table, looking sheepish but at least back to his old self. Some people in the Ministry wanted to take him to St. Mungo's for testing, in case of lingering effects of the tampered potion, but at least Dumbledore had put his foot down on that pretty quickly.
Tony shoots him a wide grin, and is pleased when the gesture is returned.
Clint finds them outside the Great Hall after everything is done. "Heard you guys are big heroes now," he says.
"Heroes is a strong word," Tony replies. "We just killed a snake. And made a really kick-ass potion."
"Slughorn says that we definitely won," Bruce adds. He looks sort of proud and sort of embarrassed, hands shoved into his trousers.
Tony slings an arm around Bruce's shoulders. "As cool as giant green monsters are, I think I prefer you like this. Much cuter."
Bruce turns a rather adorable shade of pink. "Er, thanks?"
"Gross," Clint laughs. "Hey, wanna watch me shoot quills at the First Years?"
"Hell yeah," Tony says, and as they follow Clint outside, he keeps his arm firmly around Bruce's shoulder, and is pleased when the other man allows him to leave it there.