The Boy-Who-Dungeon-Crawled

[Harry Potter AU]

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Summary: Auror Captain Nymphadora Tonks and her rookie partner, Harry Potter, are about to get caught between a rock and a heart place. Even worse, the rock is a homicidal lump of glowing geology that calls itself a "Dungeon Core"... And the heart is another bloody Horcrux.

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A spiky mop of bubble-gum pink hair came bouncing down the flight of stairs, accompanied by the woman whose head it was attached to. Usually, when a person wearing bright red robes was galumphing down towards you at speed, most people wouldn't spend time paying attention to their coiffure, but Auror Captain Nymphadora "Don't Call Me Nymphadora" Tonks had a knack for picking hairdos guaranteed to draw notice.

"Nothing upstairs," shouted Tonks. "No signs of intruders. Are you done taking that witness statement yet, Potter?"

Harry relaxed, once he saw that Tonks had managed to make it the entire way down the stairs without tripping. "Yeah, well, that's what I was trying to do, Captain," he said. "But the, uh, witness is refusing to state anything about her emergency."

The third person in the room – a short, middle-aged woman with curly blonde hair, pale blue robes and a pair of large, fluffy slippers – folded her arms tightly over her chest. "I can't talk to 'im when 'e's dragging ash and chimney soot all over me carpets! That's an emergency, right there!"

"You heard the lady, Potter," said Tonks with a smirk, as she cast a Scourgify on Harry's slightly grubby robes. "Quit dragging your ash."

Harry nodded his thanks. "What can I say? Floo travel and I have never gotten along. Frankly, it might have been easier to take the train."

Tonks folded her arms. "Rodent monster."

"Now, hold on," Harry frowned. "Riding British public transport might not be the best experience, but I wouldn't go so far as to call it a monster."

Tonks pulled her notepad out of a robe pocket and bonked him on the head with it. While Harry rubbed his head with a confused glare, she flipped open the small booklet and pointed to the few sentences written on the most recently used page. "I said 'rodent'," Tonks chided him. "Not 'rode on'. We got that much information when Mrs. Priddygump, here, contacted the DMLE."

"Tha'ss right!" Mrs. Priddygump nodded, her vehement head movement making her bob of curly hair jiggle. "It was a giant rat, it was! All slaverin' and snarlin'! It was 'orrible!"

"Go on, then," said Tonks, nudging his shoulder with her own. "Are you gonna take notes, or what?"

Harry went through the tedious motions of taking a witness statement, asking about various pertinent details – such as the witness's name, occupation, and the nature of their emergency – and jotting down the answers. ('Mrs. Vestmentia Priddygump', 'Works in an umbrella shop in Leeds', and 'Great big 'orrible rat creatures', respectively.)

"Well, the floor upstairs was free of monstrous mice, Mrs. Priddygump," said Tonks with a polite grin on her face. "Junior Auror Potter and I had best go check the basement, as well."

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Retreating from the enthusiastic Priddygump, the two Aurors – or possibly one-and-a-half, since Junior recruits didn't technically count as a full Auror – made their way down the rickety stairs to the lowest floor of the building.

"Take a look around, Potter," ordered Tonks, once they'd entered the room and found a light switch. "Tell me what you see."

"Looks like a bog standard basement, Captain," said Harry. He raised an arm, pointing from one item to another. "Washing machine, tumble dryer, ominous smoke-belching pit, old cardboard boxes, cobweb collection in the corner..."

Tonks folded her arms, giving him a firm nod. "Indeed! Well spotted, that man. Now, which of those things are not like the others?"

Harry tapped his chin. "Hmm, I'm gonna go with..." He waved his finger, performing the traditional selection procedure known as 'eenie-meenie-mynie-moe'. Finally, he made a decisive jabbing motion at one of the basement's features. "The ominous smoke-belching pit."

"Congratulations!" Tonks slapped him on the shoulder, almost knocking him over. "You win the grand prize!"

Harry's gaze darted down to his senior officer's smiling lips, then quickly back up to her eyes again. He mustered an awkward smile. "R-really? What do I win?"

"You, Junior Auror Potter, have won the honour and privilege," said Tonks. "Of going first!"

"Golly, what fun," said Harry in a voice that clearly expressed his lack of enthusiasm. "I can hardly wait. Although... Surely, as the senior officer, you should go first, Captain?"

Tonks' face crumpled in an exaggerated grimace. When Metamorphmagi were upset enough that their face fell, they didn't do it by half measures. "Shirley?! That's almost as bad as the name that Mum gave me!"

Her face lit back up in a fresh smile. "But to answer your question," she chirped, chivvying him towards the yawning hole in the floor. "Since I'm both senior and officious, I should never go first. I mean, what if it turns out that there's a gruesome death trap, down at the bottom? If I went first, all of my accumulated wealth of skills and experience would be lost!"

Harry just shook his head in defeat.

"Wasted!" wailed Tonks. "Squandered! A terrible blow to the DMLE, one from which they may never recover!"

Pulling out the shrunken broom he carried on a chain around his neck, Harry tapped it with his wand, returning it to its usual size.

Before he could mount the broom and begin the descent into the depths of the earth, a slender red-robed arm snaked out and seized his chin. He stalled, as Tonks pulled his head around, forcing him to look her in the eye. Her voice was uncharacteristically sombre, when she spoke. "All joking aside, Harry... Don't take any stupid risks, alright? I'll be right behind you, covering your back."

Harry nodded, feeling a shiver run down his spine at the touch of Tonks' warm fingers against his chin. "...Y-yeah. Don't worry about me, Tonks."

Her face returned to its default state of cheerful bullheadedness. "Triffic! I wouldn't want to have to start training a new minion, when I've just managed to get you housebroken," said Tonks, releasing her grip on his jaw so she could tweak his nose.

"...No, we couldn't have that," sighed Harry. His tone was exasperated, but the lopsided smile was quite genuine.

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Before sallying forth, Harry took a moment to think. Back at Hogwarts, he'd specialized in charging ahead with little or no preparation, but Auror training – and especially the lessons that Tonks had picked up from Mad-Eye Moody, and was passing on to him – had taught him the value of forethought.

Besides, it didn't take a genius to realize that flying down into a vertical tunnel filled with smoke, without so much as a Bubble-Head Charm, would be very foolhardy, indeed.

Feeling somewhat like Father Christmas, heading down a chimney, Harry suppressed the sudden urge to say 'Ho, ho, ho!' and cast a few spells on himself, instead. He wanted to retain as much of his field of vision as possible, as well as his ability to breathe, when he went down the smoke-filled shaft. Hopefully, he'd be able to get by on Charms.

The actual flight down through the chimney-like tunnel was mildly claustrophobic, but otherwise uneventful. Proceeding slowly to avoid colliding with the narrow, rough walls around him, Harry wasn't entirely sure how long it took; at least a few minutes worth of cautious travel, as the broomstick flies, probably no more than ten.

Finally, the oppressing sense of being surrounded by metric tons of earth lifted, as the shaft opened into a large cavern. Harry's eyebrows rose, as he saw the large expanse below him.

The wide cavern seemed to continue down and further down, longer than he could see. In the middle of the deep crevasse was a series of interconnecting stone bridges and walkways, supported by rock pillars that were both ridiculously tall and narrow. These raised paths led from a small ledge that jutted from one of the walls, out to a large, rubble-strewn stone platform, located directly underneath the chimney in the ceiling through which Harry had entered.

Far below, the flickering reddish-orange glow of active magma flows pulsed against the inky gloom. Plumes of smoke rose from the depths, spreading across the ceiling and eventually rising up through the shaft leading to Mrs. Priddygump's basement.

"Hogwarts doesn't teach much in the way of geography..." muttered Harry to himself. "But I'm fairly certain that Britain shouldn't be on top of any particularly active volcanoes."

Harry floated downwards, turning his broom in a slow circle as he scanned the room. Basic Auror training had included lessons on situational awareness, and the nooks and crannies in this cavern provided plenty of hiding places for potential hostiles: jagged boulders, stalactites jutting from the ceiling overhead like the rough incisors of a gigantic stony beast, criss-crossing rock walkways made of rock platforms balanced on colossal teetering stalagmites... Everything lit by the Lumos charm from his wand, and a fiery glow from the lower reaches of the cave.

Harry tilted his head up to look for Tonks, then quickly twisted his head back down to inspect the cave floor.

"I hope you're not trying to catch a peek up the skirt I'm not wearing, Potter," chuckled Tonks, as she arrived in the cavern on her own broom, floating down through the same vertical canal that Harry had travelled.

"Don't worry, Tonks," said Harry. Thankfully, the reddish illumination from below would make his blush harder to notice. "Anyone attempting to perv on you would be blinded by the ridiculous trousers you're wearing under your Auror robes."

Tonks gasped, clutching a hand to her chest. "How dare you belittle my amazing leg garments!"

"Well, I'm hardly a fashion expert," said Harry. "But if Lavender and Parvati saw you right now, I suspect they would have very strong words with you about what a heinous crime it is, combining bright red with orangey-yellow."

"Oi! This stylish outfit is burgundy and ochre, I'll have you know!" Tonks tried to look scandalized, but her bubbling laughter took most of the sting from the rebuke.

Harry snickered. "Shouldn't you be keeping your voice down? We're exploring an unknown area, potentially full of enemies. 'Constant Vigilance', and all that."

"Oh?" said Tonks with an amused tone of voice. "Do you think I forgot such a basic part of protocol?"

"Nah," said Harry. "I'm just wondering if you decided to cast a Homenum Revelio on the way down, and already checked for Dark wizards lurking in the corner."

Tonks rolled her eyes. "That, plus the appropriate detection Charms for finding various dangerous rodents of unusual size. Kept an eye on you while you were keeping an eye on the surroundings, as well. Good job, Potter."

Harry turned away, trying to hide his pleased smile. "Thanks, Captain." As he ran another scouting glance across the cavern, he took in the perilous maze of zigzagging bridges and narrow walkways, with the fiery pit far below. "Y'know, I'm really glad we brought brooms. This would be impossible to cross on foot."

Tonks started to smirk. "Good thinking, Harry! Gimme your broom."

"...Huh?"

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"I never thought I'd say this," panted Harry. "But this is even worse than the usual obstacle courses you force me to do!" He segued from running to jumping, as one of the stone walkways began to tilt on hidden hinges, threatening to let him plummet to his doom.

"Hey, it could be worse," yelled Tonks, gliding along beside him on her broom. "You could be doing this with old Mad-Eye as your coach! He'd be peppering you with Jelly-Legs Jinxes, and Blasting Curses, and worst of all: His special creative insults!"

Without warning, bright plumes of fire and cinders burst from the lava far below, somehow reaching all the way up to the stone walkways; if Harry had to guess, he'd suspect magic was involved. Thankfully, a Flame-Freezing Charm was enough to let him hurry through the gouts of flame without losing any eyebrows.

If there'd been any doubt about magic having been used in the construction of this place, those suspicions were put to rest a few seconds after Harry's foot landed on a pressure plate he'd failed to spot. Promptly, a large portion of the stone walkway spun around on some invisible axis, launching him into the air like a pebble from a catapult.

Tonks laughed, flying alongside him. "Relax! Just think of all the healthy exercise you're getting. Don't worry, if you take a swan dive, I'll Arresto your Momentum."

"Incarcerous!" Thick ropes shot out from the tip of Harry's wand, wrapping around another walkway as he soared past. Hurriedly clenching his wand between his teeth, Harry used both hands to grab hold of one end of the rope. With his jaws firmly locked around a length of holly, he was unable to either holler like Tarzan or scream in terror; instead, he just did his best to survive.

Swaying back and forth at the end of the conjured rope, Harry did his best to gulp down a few lungfuls of smoke-mingled air past the wand between his teeth. Then, he took a long look at the ledge he was trying to reach at the far end of the walkways.

"Oh, bugger this for a game of soldiers!"

If his hands weren't fully occupied with hanging on for dear life, he'd have slapped himself in the face.

With an awkward twisting motion, Harry managed to spin around on the rope. There was a cracking noise, and then he vanished.

Harry popped back into existence by the cavern's wall at the far end of the walkways, standing on the ledge.

"Took you long enough," giggled Tonks as she floated closer on her broom. "I was starting to wonder if you'd forgotten you're legally allowed to Apparate now, Mr. I-Used-To-Have-My-Face-On-Wanted-Posters."

Too busy catching his breath to attempt witty banter, Harry just gave her a weak glare.

"Y'know, that's the truly odd thing about this place," said Tonks, dropping down on the ledge beside Harry and dismounting. "No Anti-Apparition Wards, no broom-disabling wards." She gestured at the broomstick in her hand. "Someone went to all the trouble of building this place, excavating a tremendous underground cavern system, turning it into an obstacle course that'd make Moody applaud with whatever fingers he's got left... And then, what? They forgot to put in the final details, the ones that'd prevent people from bypassing their traps altogether?"

Harry nodded slowly. "This place is like a death trap for Muggles... Or for under-age wizards and witches, who haven't learned how to fly a broom yet, let alone how to Apparate."

Tonks' eyes narrowed, her lips twisting with distaste. "Mrs Priddygump doesn't have any kids, I already checked."

Harry shrugged. "Did she use to have some, recently?" When he noticed Tonks' glare, he hurried to continue. "Anyway, we don't know if this place has exits in other basements."

Tonks nodded at the wall of the cavern, where an open archway led into a corridor. "Speaking of exits, we should probably go take a look at this one."

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The hallway was fairly unremarkable; an unlit corridor, surrounded by a stone ceiling, walls and floor, resembling natural cave formations that had been smoothed out a little for easier passage.

Tonks slapped Harry on the shoulder. "Time for a pop quiz, rookie! Remember how our witness claims to have seen giant rats rampaging through her lace doilies?" She crouched down and examined the floor. After a moment's search, she pointed. Following her finger, Harry noticed a trail of large paw prints, vaguely rat-like in shape. "Without so much as wiping their feet on the doormat first, either. So, question: What are the most likely explanations for this?"

Harry straightened, rolling his shoulders while he mulled it over. "Well, given the evidence we've found already," he said. "We can probably rule out Firewhiskey-induced hallucinations."

Tonks nodded. "True."

Scratching thoughtfully at the faint five o'clock shadow of beard growth on his chin, Harry made a mental note to shave a bit more thoroughly tomorrow. "There's a lot of ways to use Charms or Transfiguration to create giant rat monsters, as well, although most of them would only be temporary. Might just be someone playing a prank on Mrs. Priddygump, casting Engorgio on regular rats... Or, more worrisome, someone mucking about with Dark magic."

Tonks hummed in agreement, seemingly distracted by inspecting the paw prints on the ground.

"Could be someone's been keeping an exotic pet," said Harry. "Either one of her neighbours, or possibly even Mrs. Priddygump herself; if it's an illegal creature, or she doesn't have the proper permit for it, she might have decided to pretend that it was just a pest or random vermin, rather than admit she'd bought it herself, and it broke loose."

"Always a fun possibility," said Tonks. "Although, bear in mind that people who own illegal Dark creatures rarely call the Aurors to deal with the mess if the critter escapes. Anyway, Priddygump doesn't really strike me as the type who'd want to keep a rat monster as a pet. Far too prim and proper for that sort of messiness."

"Yeah, good point," said Harry.

Tonks raised a finger in the air. "Now, what magical creatures could potentially be described as 'rodent monsters'?"

Harry started counting off options on his fingers. "Might be a Kneftrow, Osquip, Two-Tailed Chuzzlebluck..."

Tonks waved a hand. "Alright, sure. There's plenty of options. Do we have any evidence that lets us discount any of them as being unlikely possibilities?"

"Well, for starters," mused Harry. "Mrs. Priddygump just described the creature as a 'giant rat monster'. She never mentioned anything about it having more than the standard consignment of two eyes, four legs, one tail, and so on."

"Ah-ah! You're forgetting the first rule of dealing with witness statements," said Tonks with a smirk, wagging her finger at him.

"Em... You mean, 'People tell things that are untrue'?" Harry leaned his head back, trying to avoid Tonks' lethally sharp finger-poking. "Do you think Mrs. Priddygump is lying about the rat, for some reason?"

Tonks flapped her arms to the sides in an expansive shrug. "Either that, or – more likely – her testimony might just be plain inaccurate. She might only have caught a fleeting glimpse of the creature, or it was dark, or she's gotten caught up in all this jolly excitement; whatever the reason, she could be misremembering things."

Harry nodded. "So, we might dealing with an Osquip, after all? Uh, should I start conjuring up some shiny glass beads we can use as a distraction? Pretty sure they love that sort of thing."

"It's possible, but unlikely," said Tonks. "Remember when I asked you about evidence that let us rule out some of the options?"

There was silence for a moment. Then, Harry snapped his fingers. "The footprints you found! Can you tell how many legs a creature has, just by looking at the tracks it leaves behind?"

Tonks gave him a proud smile. "Got it in one, rookie! There are spells for that sort of thing, of course, but old Mad-Eye always insisted it was lazy thinking if you didn't try to get confirmation through multiple means – and that includes using Muggle methods, like the Mk I eyeball."

"Right," said Harry. "And being lazy leads to being sloppy..."

They finished the familiar Mad-Eye Moody maxim together: "...And being sloppy leads to being dead."

Kneeling down beside each other, Tonks showed Harry how to interpret the rodent tracks, pointing out the salient details. "So we can conclude that whatever creature left these paw prints, they were scampering merrily along on four legs, not six," said Tonks in conclusion. "Or eight, or ten."

Harry's eyebrows rose. "There are Osquips with ten legs?"

"Didn't Hagrid ever mention that? They're pretty rare, but yeah, there are some," said Tonks. "It's unpleasant enough to come face-to-teeth with a hairless yellow rat that's as big as a pitbull and twice as grumpy, but it's even worse when it's got enough feet to stomp on each of your toes, individually."

Harry smirked. "Is that the voice of experience I hear?"

Tonks swatted the back of his head. "Hush, you! Anyway, see those swooshy-sorta swipe marks? That's from the tail – singular, from the looks of it."

"Which rules out the Chuzzlebluck," said Harry. "Still, just because it's unlikely to be an escaped magical creature, there might be a Muggle neighbor who'd bought... I dunno, a pet Sumatran dire rat, or something like that."

As the duo turned a corner, they suddenly found themselves at the mouth of a large cavern. The corridor widened into a far broader space, with both floor and ceiling smooth enough to make the area look more like a room, rather than a natural cave. A huge and complicated piece of machinery filled much of the room, chugging away with rattling metal fastenings and hissing jets of steam, making the place seem like an underground factory.

Hunched figures, half rat and half human, slunk about on two legs carrying crates of supplies with their front limbs, or skittered quickly around on all four paws. Harry counted roughly a dozen of the humanoid rat-folk, busy with whatever work they were doing. As best he could tell in the dim lighting, most of the rat-creatures had fur in shades of brown or russet, with a few grey rat-men, as well. The chittering calls of bickering rat-creatures could barely be heard over the loud, monotonous noise of the pumping, whirring, thumping machinery.

In one corner of the room, a hulking troll-sized rat-creature plodded along inside an oversized hamster wheel. The beast was veritably rippling with muscles across its broad chest and over its three lopsided arms, thick as tree-trunks. The treadmill was connected to the machinery, presumably powering some part of it. Heavy pistons rose and fell as the machinery whirred on, the ground trembling with the vibrations.

A conveyor belt was carrying milk bottle-sized glass flasks towards a large nozzle at the end of a broad pipe, which extended from the big machine. Every few seconds, the machine would chug and churn, and a dose of glowing green liquid spurted from the nozzle into an empty bottle positioned underneath. The full bottles continued on the conveyor belt, moving to a work station where several of the rat-creatures toiled, carefully packing the flasks in sawdust-cushioned wooden crates. The air in the room had turned hazy with the cloying fumes, that burned at the back of Harry's throat.

"Somehow, I doubt that this contraption is just Mrs. Priddygump's water heater," muttered Harry.

A piercing cry rang out, audible even against the background cacophony of clanking machinery. One of the rat-creatures had glanced towards the entrance, and pointed a filthy claw at Tonks and Harry.

The other rat-men turned, and bared their yellow fangs in threatening snarls at the Aurors. They unsheathed rusty iron blades, and brandished their weapons with some semblance of skill; knives, machetes, curved daggers with serrated edges. Several of the rat-men had even tied sharp bits of scrap metal to the end of their tails, turning the whip-like appendages into literal back-alley shivs.

Tonks glanced at Harry, and nodded at the rat-human hybrids that were coming towards them with malice very obviously aforethought. "Are you going to ask to see their passport and ticket from Sumatra, or should I?"

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As combat ensued, the rat-creatures proved highly nimble and dexterous, dodging and weaving out of the way of much of the spellfire that Tonks and Harry rained down upon them as they advanced. Even so, once a few of the rat-men had been knocked unconscious or hoisted upside-down by an invisible force, the remaining creatures grew more cautious, sneaking along behind packing crates and whatever else cover they could find in the factory-like chamber.

A loud roar drew everyone's attention to the gargantuan treadmill. The rat-faced troll reached out with its three beefy arms, and tore a pair of the wooden wheel spokes to splinters with casual ease. The behemoth forced its way out through the new opening, and started stomping towards Harry and Tonks.

Pausing next to an antiquated-looking forklift, the troll-sized rat-creature ignored the chittering objections of its smaller brethren at its wanton destruction of their workplace, and wrapped a trio of meaty paws around part of the forklift's metal chassis. Grunting at the strain, the ratty troll hefted the heavy vehicle, and ripped it apart.

Wielding a third of a steam-powered forklift in each paw, the rat-faced troll continued its ponderous charge towards Tonks and Harry.

As the large beast-man reached the Aurors, Harry dodged the first hammer-blow while Tonks leapt aside, hitting the floor in a roll that brought her back up in a firing position. The two Aurors both stumbled to regain their proper footing when the floor shook, the rat-troll's improvised bludgeons leaving divots in the already cracked paving stones underfoot with each impact.

"Stupefy!" Harry's spell struck the rat-faced troll in the shoulder. Harry blinked, hesitating for a moment as he waited for the creature to fall unconscious. The rat-troll just stared at him with a blank look.

Then, one of its three upper limbs began to slump down.

"Um, Tonks? I think I managed to make its arm fall asleep!"

"Next time, try aiming for the head!" Tonks bellowed at him, flicking a steady stream of curses at her opponents. "It's the bit on top, with a face and a murderous expression on it!"

Harry flicked a string of Butter-Spreading Charms at the huge rat-creature. As the spells struck, they had little effect on the beast itself, but when they hit the mangled forklift remains in its paws, a slippery yellow layer rapidly grew across the metal surfaces. With faint 'shlurp' sounds, the improvised weapons slipped from the creature's grip.

The ratty troll howled in confused anger, and grabbed Harry with its bare paw. Picking him up with the same ease – and lack of gentleness – with which a child might heft a doll, the brute swung him by the leg like a bludgeon. The blow was wild and poorly controlled, missing Tonks and knocking over two of the human-sized rat-creatures instead.

"Nice teamwork, Harry!" Tonks cheered. "But when I told you to use your head, I didn't mean as a blunt instrument!"

"Wasn't... Argh! My idea in... Guh! The first place!" Struggling to aim properly while being swung about like a flailing ragdoll, Harry managed to tag the rat-faced troll with a Tickling Jinx. The huge creature started rumbling with deep chuckles. Wiping tears of mirth from one eye, the rat-troll finally released Harry – by hurling him away.

He sailed through the air, landing on top of the large treadmill with a 'whumph!' of expelled breath. Immediately, the wheel started to rumble into motion, turning slowly. Still winded from the impact, Harry scrambled to stay on top, or at least to avoid being thrown off. Huffing like another steam engine, he managed to get upright and start jogging along the turning treadmill.

This state of affairs soon got even more precarious; one of the rat-men had noticed Harry's current predicament, and started climbing the wheel. It jumped onto the side of the rotating treadmill that was rising, speeding the rat-creature's ascent as the wheel helped lift it towards Harry.

Panting with exertion, Harry cast a hurried glance around. Finding nothing he could use to deal with the rat-creature, he decided to go with plan B. Now, he just had to come up with a plan B.

Harry whipped his wand toward the rat-man and cast a quick barrage of Sticking Charms on its paws, glueing the creature to the side of the treadmill. Tossing a final Blasting Charm straight down the middle between the rungs of the treadmill, Harry spun in place, and vanished with a 'pop'.

Reappearing on the other side of the room, back on terra firma, Harry promptly collapsed in a pile with a pained yelp. Disapparation was definitely not supposed to be practised while running on top of a giant hamster wheel, but it was probably better than trying to jump down from that height; he'd prefer the risk of Splinching over the risk of splatting.

Gingerly getting back on his feet, the stabbing pain in his foot informed him that he'd probably lost a few toes in the process. He'd have to look for those, later.

Looking back at the treadmill, he saw a new flavour of pandemonium spreading amongst the rat-creatures. His parting salute had blown the treadmill's central axis to smithereens, causing the huge wheel to wobble free from its broken housing. Currently, the treadmill was trundling its way across the factory floor, smashing crates and shattering bottles, and squashing rat-men who were too slow to leap away. The rat-creature that Harry had stuck to the wheel was still attached, getting repeatedly crushed against the floor whenever the wheel rolled over on top of the rat-man. The increasingly flattened-looking man-rat made a sad squeaking noise each time it was run over.

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Meanwhile, Tonks was holding her own against five of the rat-creatures, even as they tried to back her into a corner, up against the noisy machinery. Taking out a couple of them with Stunners and a third with a Full-Body Bind, she was caught by surprise when one of the remaining rat-men made a desperate lunge at her. The snarling rat-creature stabbed its long knife past the hurried Shield Charm she'd cast in response. Tonks drew a breath of relief when the rust-pitted blade missed her face by inches.

Then, as she tried to bring her wand around to teach the rat-man what a Nose-Crushing Hex at point blank range felt like, her arm refused to budge far enough. Her eyes widened as she realized that the knife had gone through the sleeve of her Auror robes, pinning the crimson fabric to the side of the big machine.

Baring its vicious-looking teeth in a savage grin, the rat-creature grabbed hold of her other wrist, blocking Tonks from punching the ugly thing. The bipedal rat-man clearly had some basic melee combat skills; it had positioned itself at an angle beside her, making it almost impossible for her to kick it in any vulnerable areas, and one glance at the filth and grime covering the rat-man's spike-studded shin guards was enough to make her reluctant to try stomping its toes. Even if that manoeuvre worked, she'd walk away with a limp at the very least, and more likely with a fresh dose of tetanus.

The remaining rat-man stepped up, chittering with excitement. It raised the ugly, jagged sabre in its paw, ready to slit the pink-haired Auror Captain's throat.

Tonks braced herself, readying to try a high kick that might knock the weapon out of the advancing rat-man's grip. Before she could make the attempt, the first rat creature stopped the newcomer, shoving its fellow rat-creature back before it could strike.

"Let go!" growled the stab-happy rat. "Kill-kill man-thing!"

"Yesss," snarled the rat-man with leadership ambitions, nodding its head at one of the machine's leaky steam valves. "Boil-fry man-flesh! Cook! Eat!"

The disgruntled rat-creature's face twisted into an ugly smirk. It started making squeaky cackling noises of sadistic glee, helping to hold Tonks in place, as the bossiest rat-man reached out and grasped Tonks' head by her hair.

With slow but inexorable force, the rat creature pushed Tonks's face closer and closer to the burbling steam valve. The machine's pipes rumbled and hissed, seconds away from disgorging another burst of scalding hot steam.

Grunting with effort, Tonks managed to tilt her wand a few degrees in the right angle. "Protego!"

A billowing white torrent of searing hot steam burst from the seams of the great machine, striking the Shield Charm that Tonks had cast in the nick of time. The shimmering force-field deflected the steam, redirecting it past Tonks and straight towards the hands and face of the two rat-men.

Agonized screams in two different inhuman voices rang out, as the paws clutching Tonks fell away.

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As Harry turned away from the sight of hapless rat-creatures being mauled by their own treadmill, he witnessed Tonks finishing off a couple of rat-men by the side of the big machine.

His eyes widened when he saw the huge, lumbering form of the rat-faced troll, sneaking up behind Tonks. A beast that big shouldn't be able to muster much in the way of stealth, but the constant clamor of the engines and pistons was more than enough to drown out its heavy footfalls.

"Tonks! Look out, behind you!"

Taking a quick look over her shoulder, Tonks spun in place and disappeared, Apparating to safety barely a split-second before the rat-like troll's huge paw could grab hold of her.

Adrenaline pumping through his body, Harry felt his fear give way to anger. He shot a string of curses and combat hexes at the lumbering giant, but the troll-sized rat-creature's thick hide seemed to be just as resistant to directed spells as a regular troll. Desperate for something, anything, he could use as a weapon, Harry's eyes fell on the conveyor belt.

One quick "Accio bottle!" later, a flask of luminous green goo was soaring through the air towards him. Thankfully, he had plenty of practice aiming for small, fast-moving targets, both from the spell battles he'd been survived during his Hogwarts years, from Auror training, and especially from his time on the Gryffindor Quidditch team.

"Oi! Ugly! Over here!"

Hearing his frantic cry, the rat-like troll glanced at him over its shoulder. Harry capitalized on that opportunity for all it was worth, using a Banishing Charm to hurl the flying bottle at the monster.

A comical look of affronted surprise spread on its rat-like face, when the flask flew straight into its nostril and stayed there.

Harry wiggled his wand, its sparking tip drawing a fiery W-shaped arc in the air, and then jabbed the length of holly at the rat-troll.

"Pulmonarinflaro!" A jet of canary yellow light shot out and struck the monster in the back. Seconds later, the beast began to swell up.

The jinx he'd cast was a prank spell that he picked up from the Weasley twins; it was designed to emulate the bout of accidental magic that Harry had once used to blow his Aunt Marge up like a balloon - it made the target's torso inflate, turning them into a living beach ball for a few moments, before expelling all the excess air from their body in a great gust of wind. As a safety measure, the spell also increased the elasticity of the target's body, which protected them from most of the harm they'd otherwise suffer from undergoing such sudden inflation.

Even so, the Organ-Inflating Jinx usually caused plenty of collateral damage once the victim deflated, due to the expelled air making them zoom around like a loose balloon; this event would also produce a loud belching noise, which someone theoretically might find humorous.

You also had to be careful not to mistake it for the much more dangerous - not to mention lethal - spell known as the Organ-Expelling Curse. Of course, even a jinx could be harmful under the right – or wrong – circumstances.

As the spell forced the troll-sized rat-creature to draw vast gulps of air into its lungs and stomach, its lengthy continuous deep breath made a noticeable whooshing sound. The flask sticking out of the ratty behemoth's nostril stayed where it had gotten lodged for a brief moment, looking for all the world like a bubble of glowing green snot.

Then, much like a cork shooting out of a champagne bottle, but in reverse, the flask vanished into the monster's nose with a 'ssshlump!' noise.

Harry wasn't sure what the shining green fluid in the bottle might be, or what effect it had when ingested by a living creature, but he'd seen some of the flasks shatter on the floor and against the side of the machine; going by the way that the device's metal parts had started hissing and smoking, while the green muck bubbled profusely, he had a strong suspicion that the liquid wasn't some new kind of moisturising skin lotion.

And now, a whole bottle's worth of the hazardous green fluid had been sucked down inside the ratty troll, most likely splashing out in its lung or its gullet.

For a moment, the rat-troll just stared at him, dumbstruck. Then, it started groaning, clutching at its chest.

There was a loud noise - it was hard to tell if it was a popping sound, or a wet squelch - and the number of rat creatures in the room dropped by one.

Well, the number of living and intact rat creatures, at any rate.

The spectacle of a huge rat-like troll liquefying within seconds was a rather effective distraction, it seemed. Harry didn't even notice the approaching threat, until something impacted his shoulder, jolting him out of his morbid reverie.

"Oi! No dawdling in the line of fire, Potter!" Tonks shook his shoulder again, for emphasis this time. "No doodling, either, or we'll end up with a squiggle of fire!" Her exaggerated scowl faded into a more sombre expression. "Seriously though, you need to keep your head in the game until all opponents are dealt with."

"Yeah, I know," said Harry, giving her his most apologetic lopsided smile. "Sorry about that. Is the fight over, then, if you've got time to be raking me over the coals?"

Tonks turned away from him, jabbing a thumb at a couple of hog-tied rat-creatures. They were currently dangling upside-down by a conjured rope that had been wrapped securely around a wide metal pipe close to the ceiling. "Yeah, um, I got the last of them, while you were busy watching paint dry."

"That's not paint," said Harry. "That's what's left of the... Rodentroll? Trolldent? Whatever, the rat-faced troll-sized thing."

The Auror Captain scrutinized the festering puddle of molten flesh and green ooze. "...Huh. Still quite colourful, though."

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Deciding to deal with their captured enemies later, Tonks and Harry made quick work of summarily stunning every surviving rat-creature, making sure they were tied securely enough that they wouldn't be able to escape, even if they woke sooner than expected.

A cursory search of the large room yielded no further surprises. They did take a moment to collect a few sample bottles of the unknown green liquid that the machine was producing. Harry noted that the flasks had labels glued on the front. Each bore a crude, triangular logo or symbol on it, vaguely reminiscent of a rat's skull.

At the far end of the room, opposite the wall with the doorway where Tonks and Harry had entered, was another exit. A large, imposing stone door, embossed with an intricate pattern of intertwining lines, and a set of massive metal hinges along one side.

Tonks cast a series of detection spells and trap-revealing charms at the portal, before carefully rubbing a hand over the swirling ornamental design.
"What do you reckon this is supposed to represent?"

Harry leaned his head to one side, then the other; sadly, the pattern failed to spontaneously start making sense. "Vines, maybe? Could be Mrs. Priddygump's gardening shed, in there."

Tonks snorted. "Or it might be a room full of pipes, connected to that big machine over there." She turned to look at Harry, her lips curving up in a grin. "Why, it might even be-"

Harry groaned. "Please don't say snakes! After dealing with Death Eaters for years, I've seen enough of those blasted things to last me a lifetime."

"If it makes you feel better, we can just call them serpents," said Tonks with a grin. "Or garden hoses with attitude."

"Yep, that topic is well and truly exhausted," grumbled Harry. "Feel free to drop it, any time now."

"And if it's one of the really poisonous ones," chirped Tonks. "We could call it a Gryffindor rope-skipping rope."

"Wait..." Harry scrunched up his face in mock concentration, tapping his chin. "Do you call 'em poisonous when you shouldn't bite them, and venomous when you shouldn't let them bite you? Or is it the other way round?" He leaned closer to Tonks, flipping up a hand with two fingers extended, in the British equivalent of a similar gesture that Americans would only bother using one finger to do. "Or should I just say 'bite me'?"

Tonks guffawed. "You should ask Hermione about those big difficult words, when we get out," she said, waggling her eyebrows. "She'll probably give you a book on the subject, and reassure you that this one definitely won't bite."

Harry snorted. "Unless it's one she got from Hagrid."

A quick 'Alohamora' dealt with the issue of locks readily enough, but the door was large and heavy enough to make the act of simply opening it something a challenge. Harry braced his feet, leaning against the door as he struggled to push it open.

Tonks watched him grunt and sweat with clear amusement. "You want a Featherweight Charm with that, macho man?"

Harry's embarrassment was thankfully curtailed by the door's sudden surrender. Stumbling slightly as he almost fell into the room, when the door swung open with a noise of stone grinding against stone, Harry straightened, dusting himself off, and took a look around.

Statues of reptilian monsters lined the walls of the elongated chamber, like an honour guard watching over the path leading to the raised dais at the far end. Some had snake heads on muscular human bodies; some were humanoid from the waist up, with broad snake tails in place of legs; and some were odder still.

Harry recognized several of them from his studies in Care of Magical Creatures; most of these specimens would be dangerous enough to have Hagrid cooing and clapping his hands in delight at seeing such 'poor, misundehstood li'l critters', if they'd been living flesh and blood. There were marble statues of Yuan-Ti warriors armed with wicked-looking polearms, broad-chested Serpentinotaurs whose skin was coated in bronze scales the size of saucers, a pair of Naga with gleaming gemstones for eyes, a nest of Cobrascal Pygmies taking aim with their blowguns, double-headed Amphisbaena that lay coiled and ready to perform their dreaded 'Rolling Hoop of Death' attack...

"Cor, will you look at that," said Tonks, peering closer at one of the guttering torches along the wall; they'd burst alight when the door was opened. "Chartreuse flames, no less. I might take one or two of them home, give 'em to my parents for Christmas."

"Really?" Harry raised an eyebrow. "Don't they already have this amazing new invention called indoor lighting?"

Tonks wrenched one of the torches free from its sconce with a grunt. She tapped it with her wand twice, first freezing the flame, then shrinking it to matchstick size. Slipping the purloined light source into one of her robe pockets, she turned back to Harry and shrugged. "Sure, but this could work as a compromise between Dad's Hufflepuff yellow and Mum's Slytherin green."

The air in the chamber smelled stale yet spicy, the strong scent of dust and cinnamon tickling Harry's sinuses. The ceiling was high and arched, supported by tall pillars that had been carved with twisting patterns of swirling runic script.

Not for the first time since joining the Aurors, Harry regretted that he'd never studied Ancient Runes in school. Not that he'd ever admit as much when Hermione was within earshot, of course, or he might never escape the mountain of reference books and runic dictionaries she'd be sure to bury him with.

Still, his lacklustre understanding of archaic alphabets left him with no idea what all the writing on the pillars meant, unless it turned out to be a message along the lines of: 'Wow, I love curlicues, look at how great they are'.

Harry and Tonks slowly stalked through the chamber, keeping a cautious eye out for any sudden movements. As they reached the furthest end, Harry gestured at the elaborate decoration on top of the podium. "I guess there must be something special about that marble pedestal, since this whole place seems like it was built to protect it."

Tonks tilted her head to the side in thought, scratching her nose. "Hmm... Are you sure it's a pedestal? Looks more like a plinth, to me."

"Pedestal, plinth..." said Harry with a shrug. "What's the difference?"

"If it uthed to be a frog before you kithed it," lisped Tonks with a wicked grin. "Then it'th motht likely a plinth."

Harry groaned, covering his eyes with his hand. "I can tell you're related to Padfoot. By the way, I think that joke only works if you say 'flog' instead of 'frog', if you're going to say 'plinth' instead of 'printh'."

Harry noted that the pedestal (or plinth, possibly) was topped with a copper ornament, shaped like a pair of clawed hands, green with verdigris. The claws were clasped around a glittering crystal orb, that floated a few inches above the greedy reaching hands.

In an instant, Harry and Tonks both crouched down and whipped their wands into a combat stance, as they felt the chamber starting to rumble. The crystal ball began to glow, a corona of emerald lightning crackling around it.

A harsh rasping voice emanated from the shining orb, filling the chamber with hissing echoes. "Intrudersss! Who daresss to trespasss in the sssanctum of the Dungeon Lord VoldeCore?"

Tonks turned her head, shooting a wry glance at Harry. "Looks like you got your wish, Junior Auror Potter," she drawled. "Now, we're flogged."

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