Hermione was mad at Tom.

Learning how he had made the horcrux still felt like a betrayal, even though he'd done it years before she'd even been born. It was just evil of such a different caliber than she had thought Tom was capable of, and she didn't like that she was now reevaluating her pseudo-friend at every turn in this new light.

Tom was, at least, trying to help her brainstorm how to defeat the dementors, as he'd promised to do so. He had explained his main theory: because the dementors fed off of souls and held the soul scraps inside of them that they consumed, they could probably be destroyed by anything that could also destroy a horcrux.

But therein lay the problem.

"You say that like it's so simple, so easy," Hermione said, giving Tom a pointed look. "Horcruxes are supposed to be nearly indestructible."

"That itself means that they're not indestructible," Tom argued. "You've threatened me with the destruction of the diary each time you've pulled me from it."

"That's because I'm extraordinarily lucky to have a goblin-made sword with basilisk venom imbued in it," Hermione said. She made a face. "I am not exactly going to go after dementors swinging a sword, Tom. It'd be mad."

Tom smirked. "Why not? I bet you could get a medieval ghost to teach you sword fighting. We could commission you dementor-resistant armor, get you to take lessons, the whole cauldron."

Hermione rolled her eyes. "What else is there?"

"Well, a horcrux isn't destroyed unless the vessel it's in is damaged beyond repair," Tom said. "And they tend to protect their vessels fairly well. You'll need something that will destroy anything."

"Could I burn the diary?" Hermione asked. "It's made of paper – it should burn, I would think. And that would destroy it."

"I doubt it," Tom said, raising an eyebrow. "Making an object a horcrux lends it a certain amount of protection. Regular methods of destruction aren't likely to prevail unless they overpower that Dark magic."

Hermione didn't like the look in Tom's eye. She had no intention of learning Dark magic, thank you very much.

"We burned up the piece in Harry with a purification ritual," Hermione recalled. "That might work…"

"Yes, on Beltane," Tom said dryly. "If you think you can get all the dementors into one ritual circle for an extended period of time on Beltane to be purified away, by all means…"

Hermione shot him a nasty look.

"What's your idea, then?" she asked him. "I know you have one that's better than sword-fighting them."

Tom looked at her reflectively for a moment.

"You weren't far off with your idea of burning," he said. "You'd just need a different type of fire."

"What, like Gubraithian fire?" Hermione said, her jaw dropping. "That's – I really don't think I could cast that—"

"No," Tom said, rolling his eyes. "Everlasting fire just doesn't go out. You'd need a Darker fire, a type of fire that consumes and destroys everything in its path."

"Like what?" Hermione wanted to know.

His eyes gleamed. "Like Fiendfyre."

He looked at her, anticipatory. Hermione gave him a flat look.

"Are you waiting for a dramatic reaction?" she asked.

Tom shot her a dark look.

"I was anticipating at least some reaction," he said snidely. "Most people aren't nonchalant about Fiendfyre."

"I don't know what Fiendfyre is," Hermione said patiently. "I don't study the Dark Arts as a hobby, Tom."

Tom looked like he wanted to object to that, before dismissing it and setting it aside.

"Fiendfyre is a sort of cursed fire," he said. "It's immensely powerful, and it can't be extinguished by water of any sort. It contains a sort of sentience, and a continuous desire to burn anything it can. It can chase after people and incinerate on mere contact."

"That sounds extraordinarily dangerous," Hermione said, eyes wide.

"It is," Tom admitted. "It's a difficult spell, and it's very difficult to control. You need to have a very high level of power to do so, really. And if you lose control, the fire comes after you, too."

"I'm fourteen," Hermione pointed out. "I'm three years away from reaching my magical maturity. If adult wizards have trouble controlling it, there's no way I have enough of a power store to do so right now."

"Cursed fire is our best bet for destroying soul bits," Tom insisted. "If not Fiendfyre, you could try Devil's Fire."

Hermione rolled her eyes. "What, exactly is Devil's Fire?"

"It's a sort of black fire you conjure as a test for people," Tom explained. "It's kind of protective. People can only walk through it if they're loyal to you and mean you no harm. Otherwise, they're burned to ash within moments of entering the flames." He paused. "It's not as uncontrollable as Fiendfyre, but it's also more limited. We'd be relying on the dementors to keep trying to come after you, even after seeing their brethren burn up on trying."

"Dementors are evil, not dumb," Hermione said with a sigh. She gave Tom a grudging look. "So Fiendfyre's our best bet, then? And I'll just have to figure out how to make it work?"

"Apparently so," Tom said. He paused, considering. "You know, I bet Voldemort taught his closest followers how to cast it. If you were to quietly approach—"

"Absolutely not," Hermione said firmly, shutting him down. "This is my mission. You and I are the only ones who are going to know."

Hermione dwelt on the matter in the back of her mind for a few days, letting it stew while she drilled herself on Ancient Runes and Arithmancy. Eventually, she came to an impasse, and it was with a sigh she stood up from a sofa in the middle of the Slytherin common room, stretched, and headed off toward the great glass window peering into the lake.

The tables and seats near the glass of the lake were not popular for students relaxing or doing homework, as there was always a faint chill emanating from the glass. There were several small tables set up for chess at the window, though, where the faint green glow helped cast a light on the boards that made the pieces look more dramatic, with slightly amorphous, shifting shadows, and the players ended up looking more intimidating in the fluid light as well.

Slytherins were very appreciative of their aesthetic, after all.

Draco and Theo were playing a game against each other. They both seemed very intent on the game, neither one taking his eyes from the board as she approached the table, watching.

"Want to play winner, Hermione?" Theo asked, not lifting his eyes from the board.

Hermione's lips quirked. "Not exactly. But I'll watch to the end."

She summoned a chair from a nearby unused table and sat to watch, curious.

Hermione wasn't much of a chess player herself; she knew how the pieces were supposed to move, and what the end goal of the game was, and that was about it. She was spectacularly bad at chess strategy, something that constantly frustrated her – expert chess players held multiple complicated strategies in their head at one time, and Hermione was more the kind of person to pick one strategy and charge after it full-tilt, ignoring all the others and adapting on the fly.

And while that strategy worked fairly often in real life, it meant she was absolutely dreadful at chess.

From what she could tell, Draco was winning; he was up a knight and a pawn of Theo's. They continued quietly ordering pieces around the board for a while, with few battles fought, until Theo smirked widely, ordering a pawn forward to capture.

What followed was a fierce series of duels for control of the center of the board; Theo's pawn took Draco's pawn, Draco's knight took Theo's pawn, Theo's bishop took Draco's knight, on and on and on. By the time the carnage had stopped, both boys had lost several pieces along with their queens in the fray.

Draco was looking disgustedly at his shattered pieces at the side of the table.

"Was that really necessary?" he demanded.

"No," Theo said. "But it makes it easier."

It was quickly clear that Theo had more practice playing without his queen than Draco did; Draco's efforts turned toward trying to get a pawn promoted as rapidly as possible, while Theo maneuvered his few remaining pieces into position.

"Checkmate," he said, sitting back with satisfaction.

"Ugghh," Draco groaned, as his king threw his crown on the ground. "Good game."

"Good game," Theo agreed. He grinned at Hermione. "Sure you don't want to play next?"

"Entirely," Hermione said, her tone dry.

The boys set about putting their sets of pieces away. After the game had ended, the pieces had begun rebuilding themselves from the carnage, as if an automatic repair charm had been triggered. Each boy had a fancy box in which he kept his pieces, where they were encased in velvet lining and carefully put away.

"What brings you over here, then?" Theo asked. "If not chess?"

Hermione bit her lip.

"I wanted to get the two of you alone to ask you a question," she said, glancing at them both. "Here probably isn't the best place, though. It's kind of exposed."

Draco's eyebrows rose.

"You want to ask a question that you're uncomfortable asking in the Slytherin Common Room?" he repeated. His eyes gleamed with something that looked like excitement. "Is it scandalous?"

"Umm," Hermione said. "Not exactly."

Draco pouted, then looked thoughtful.

"Is it Top Secret?" he asked. "Top Secret gossip that absolutely nobody can know?"

"I wouldn't call it gossip," Hermione equivocated, "but I'd say it might involve Top Secret matters, yeah."

Draco looked curious and excited, while Theo looked wary.

"Where do you go to discuss secret things?" Hermione asked, looking from Theo to Draco and back. "Do you know a place?"

"Generally it's just the boys' loo in hushed voices, but I get the feeling that won't exactly serve our purpose here," Theo said dryly. "I have an idea, though. C'mon."

Theo led the way out of the common room into the hallways. He took them down several stone corridors, twisting them deep back into the far recesses of the school dungeons, where there were abandoned classrooms and chambers that weren't used anymore. He picked one seemingly at random, ushering them both in before closing the door and using a Locking Charm, while Hermione lit a couple torches that were placed around the room.

"This good?" he asked.

"Perfect," Hermione said, nodding. "Thanks."

"Now," Draco said, his eyes gleaming. "What's so secretive and special and important that you wanted to talk to us about it in total isolation?"

Hermione tilted her head, considering.

How did she want to play this…?

There were a couple ways to approach the issue in question. She considered using obfuscating and subtle Slytherin language to talk around what she wanted without outright saying it, but it was a topic that she really couldn't afford for there to be any misunderstanding about. She gnawed on her lip, thinking, before glancing up at Theo.

"We're entirely isolated and completely alone?" she questioned.

"Completely," Theo assured her. "I put a hex on the door, too, so we'll know if anyone tries to eavesdrop."

"Good." She turned back to Draco. "In that case, I want to ask if the Dark Lord taught your fathers how to use Fiendfyre, and if he did, where he did so."

Draco's reaction was everything she hoped for from her blunt speech – his eyes went wide, his face went pale, and his jaw dropped. Theo's own eyes bulged, and he looked like he was about to have a heart attack.

"Y—y—you want to—"

"Are you mad?" Theo hissed, cutting off Draco's stuttering. "Just casually bringing up—"

"That's why I made sure we weren't going to be overheard," Hermione shot back. "Do you think I'm an idiot?"

"Given you're bringing up Fiendfyre in school, I think yeah, there's a fair chance—"

Draco's eyes were large and staring at her. He seemed thrown by the fact Theo was railing at her for asking about Fiendfyre in school but didn't seem surprised by her asking at all.

"Why?" Draco asked. He looked stunned. "Why are you asking about Fiendfyre, Hermione?"

"I'm curious," Hermione said coolly. "And I thought you might have answers."

"I don't know why you'd think we would have answers," Theo sneered

"I have it on good authority that the Dark Lord taught his Inner Circle how to cast Fiendfyre," Hermione said, folding her arms. "Especially to his old school mates."

Draco looked puzzled, while Theo went pale.

"How do you know that?" Theo whispered.

"The Dark Lord went to Hogwarts?" Draco asked. "Really?"

"Are you sure you want to ask that?" Hermione said to Theo. "Are you sure you want to know the answer?"

"Wait, I thought the Dark Lord went to Durmstrang," Draco said, frustrated. "Isn't that where he learned all the Dark Arts?"

"Shut up, Malfoy," Theo snapped. His eyes didn't leave Hermione's. "The Dark Lord went to Hogwarts."

"He graduated with Theo's father, here, even," Hermione said, her eyes also not leaving Theo's. "They were a crew before ever graduating, though they called themselves something different back then."

Draco was looking back and forth from Theo to Hermione with wide eyes.

"Really?" he asked. "Nott, your Dad went to school with the Dark Lord?"

"What did he call them?" Theo asked her, his voice deadly. "What did they call themselves, Granger?"

He was challenging her as some sort of test, she could tell. Her lips quirked up.

"Have you forgotten?" Hermione asked, her eyes glinting. "They called themselves the Knights of Walpurgis, Theo."

There was a stunned silence. Draco still looked puzzled.

"What's a Walpurgis?" he asked.

"It doesn't matter," Theo snapped at Draco. He turned to glare at Hermione. "Yes, okay? He taught them to use Fiendfyre. Or at least, he taught my father. I don't know about Lucius Malfoy."

Theo turned to look at Draco, who looked uneasy.

"I—I don't really talk to my father about his previous activities," he said. "He doesn't discuss them openly. It was a traumatic time for him, being under the Imperius Curse for so long like that, and he tries not to remember—"

Both Theo and Hermione rolled their eyes.

"Where did he teach them, Theo?" Hermione asked. "For a spell like that, you can't exactly quietly practice it in your dorm room."

"No, you're right," Theo said. He frowned, considering. "I can say that recent followers learned in giant fields they blocked off – there's one on the Nott Estate, hidden far inside the wood, and everything there is still scorched and burned from when the three Lestranges learned."

"The Lestranges?" Hermione asked.

"Rodolphus and Rabastian Lestrange," Draco told her. He looked puzzled. "They're in Azkaban now. Though, I thought there were just the two Lestranges who were Death Eaters – the brothers."

"Your aunt," Theo said incredulously. "Bellatrix. She married Rodolphus and became Bellatrix Lestrange. How do you not know this?"

"I know that she married him!" Draco said defensively. "I just—I didn't think she took his name. The Most Ancient and Noble House of Black is higher up than 'Lestrange', isn't it?"

"I don't know. But that's what people called her—"

Hermione took a brief moment to reflect on the subtle sexism of wizarding society.

"—and regardless," Theo continued, rolling his eyes, "that's who I meant as the third."

"Aunt Bella…" Draco said again, an expression of surprise echoing on his face. "She learned to cast Fiendfyre, Theo?"

"Merlin, Draco, did your Dad honestly tell you nothing?" Theo wanted to know. "Yes, she could cast Fiendfyre. She was one of the most powerful bloody witches in the Dark Lord's army. I don't know if there was a Dark curse known that she couldn't cast."

"She was locked up by the time I could remember anything," Draco protested. "Mum only ever talked about her childhood memories with her sisters – none of the recent ones."

Hermione was considering, frowning.

"If the land is still scarred, it's not like they could have used the Quidditch Pitch to practice around here while they were at Hogwarts," she said. "Someone would have known."

"Of course." Theo gave her a look like she was crazy. "Scars from Fiendfyre don't just heal, Hermione. The earth is still cursed."

"Wait, are you trying to find a place to cast Fiendfyre around here?" Draco said, his jaw dropping. "Are you going to try and learn?"

"Are you insane?" Hermione snapped, giving Draco a sharp look. "I'm fourteen. Do you think I'm mad? Grown adult wizards can't cast that successfully, to say nothing of the danger it would present."

Draco looked thrown.

"Why are you asking, then?" he wanted to know.

"Research," Hermione said promptly. "I'm curious."

Draco was looking at her skeptically, while Theo was looking at her in complete doubt, obviously not buying a bit of her story.

"Can't you ask your source?" he sneered.

Hermione raised an eyebrow. "I'm sure I have no idea what you mean."

Draco seemed to be contemplating while Theo and Hermione had a stand-off, thinking hard while they glared at each other.

"Fiendfyre's the cursed hellfire, right?" he asked. "With the animals that destroy everything in their path?"

"Yes," Theo said shortly. "If you lose control."

"You'd need a big place, then, to let them really run free to make sure you were doing it right," Draco mused. "Probably as long as the Quidditch Pitch at least, with no ceilings, or at least ones up very high… and if you didn't want anyone to catch you, it'd have to be a place where it was all dirt or stone, right? So no one would notice the sudden lack of vegetation…" He scrunched his face up. "It's not like you could do it in the Great Hall, though. Does Hogwarts have old dueling halls hidden around somewhere he might have used?"

Hermione's eyes flew wide open at his words.

Oh…

The idea was rapidly forming just as abruptly as it crashed into her – a long place, with high ceilings, stone floors and walls, where she'd had a 'duel' once before...

She doubted it was the same place Tom would have used – it would have been guarded by a newly-made ghost back then, after all – but it would work all the same.

"There might've been," Theo was saying, frowning. "I think it's more likely he just took them deep into the Forbidden Forest, though. Practicing inside anywhere – that'd be risky."

"You're probably right," Hermione agreed. She looked sideways at Theo. "Did you father ever teach you?"

"Fiendfyre?" Theo gaped at her. "No. No. Merlin, Hermione, I'm your age too – no one alive our age could cast Fiendfyre successfully. To even attempt it would practically be suicide."

"Oh. Right," Hermione said. "I forgot."

Theo was still looking at her like she was mad, but Draco was looking at her very thoughtfully.

"Are you learning the Dark Arts, Hermione?" he asked her.

"Absolutely not," Hermione shot back. "I'm insulted you would even ask."

Draco's eyes gleamed.

"Have you already learned the Dark Arts, then?" he asked, smirking. "Or are you going to learn the Dark Arts soon?"

"Of course not. I was curious. It was an entirely academic inquiry," Hermione said, annoyed.

"Are you sure?" Draco said. "It sounds like—"

"This is a ridiculous line of conversation, and it is now over," Hermione informed him. She tossed her hair and nodded her head to both boys. "Thank you for your time and input. I appreciate it."

"Of course," Draco said. He was smirking wider now. "Anytime."

"I'll just not mention any of this to my father, shall I?" Theo said dryly. "It'd probably make him only more eager to arrange a betrothal contract between us."

"Why Theo," Hermione said, batting her eyelashes. "And here I thought you cared."

Theo snorted while Draco laughed, and the three left the old classroom to head back to the common room together.