A/N:

I've always loved crossovers, especially if they involve Harry Potter. However, when it came to PJ/HP crossovers, I never really found one that I really liked. So I decided to write my own.

I'll only do the disclaimer once, because any more than that and it's annoying and pointless: I do not own Percy Jackson and the Olympians, nor do I own Harry Potter. (Duh.)

Chapter 1

Professor Minerva McGonagall sipped her tea, thinking what a marvellous morning it was, and how fine it would be to take a stroll around the lake after breakfast, followed perhaps by an hour or two of reading in the sunny and blissfully quiet library of Hogwarts.

She thought that, but didn't really expect any of it to come to pass. The problem with being a teacher, you see, was that after over thirty years of doing the job, you tended to develop a sense of just how dramatically wrong you were to think Excellent, there can't possibly be anything left to worry about right now, when bam!, something worth pulling your hair out for magically appeared.

She ought not to find it surprising, Minerva usually thought dryly. This was a school of magic, after all. But she'd had a summer full of frantically gathering data concerning impending first years, calming hysterical house-elves after a lack-of-flour crisis, supervising the long process of removing all traces of the Triwizard Tournament (when was someone going to invent a spell that would just *poof!* anything that was wrong with your life?) and, oh! Of course, that little matter of Lord Voldemort returning a couple of months ago, which caused the fractured remains of the Order of the Phoenix scrambling for wands, allies, or clothes, depending on whether Dumbledore's message had reached them in the middle of the night.

So in fact, Minerva McGonagall was thinking that her summer had been really quite poor, and nothing short of a Death Eater attack could make it any worse.

She was wrong.

Albus Dumbledore cleared his throat, and everyone present at the staff table turned to look at the headmaster.

"It may interest you to know that, following my failure to find a suitable Defence Against the Dark Arts teacher, Minister Cornelius Fudge has seen fit to appoint one of his choice - as indeed he is entitled to do if the headmaster did not succeed-"

"Oh, come off it, Albus!" Minerva interrupted, waving her teacup impatiently. "We all know perfectly well it wasn't your fault. The job's jinxed!"

Several of her colleagues nodded and murmured in agreement, but Dumbledore continued in his usual mild tones.

"Nevertheless, Cornelius has chosen someone as the new Defence teacher. Her name is Dolores Umbridge, formerly Senior Undersecretary to the Minister himself."

Minerva almost spat out her tea. After swallowing it with difficulty and scalding her tongue, she rasped out.

"Not that awful woman who keeps insisting that muggle-borns aren't worthy of attending Hogwarts?"

"Not the one who seems to be on a personal crusade to make glittery pink cats the national emblem?" Pomona Sprout, her usually kind face twisted in disgust.

Dumbledore's eyes twinkled in a way only those who knew him well - which Minerva did - could have spotted, and she could have sworn he looked amused.

"The very same." he confirmed. "She will arrive the day before term starts, and I trust you will all give her a very warm wel-"

"I hate that woman." Minerva muttered, making no effort to keep her voice down.

"A very warm welcome." Dumbledore repeated calmly. There definitely was a twinkle there, Minerva decided.

She quashed the juvenile urge to groan, and settled for primly setting her teacup down on the saucer, but stabbed her fruit salad with uncustomary venom. In doing so, Minerva noticed a slow grin spreading across Pomona's face. She almost got annoyed at her friend, too. What could possibly draw a smile when that godawful excuse for a woman was coming to teach at Hogwarts?

"What?" she snapped, more sharply than she'd intended.

The grin on the Herbology teacher's face widened.

"Oh, can you just imagine what the Weasley twins are going to do as soon as she tries anything? It won't be school anymore, it'll be anarchy."

Minerva considered the piece of apple speared onto her fork. She recalled all the incidents she'd unfortunately had to witness during the twins' time in the school. Dungbombs, Slipping Charms, Stalking Parrots (she still teased Severus about that) and...oooh, that time with the broomstick jinxed to whack someone in the face as soon as they tried to mount it. A faint smile stretched her thin lips. Perhaps there was a bright side to this, and one that even, say, Trelawney and her hogwash prophecies couldn't ruin.

Actually, speaking of Trelawney...

The Divination teacher had, for once, deigned to descend from her lofty tower to breakfast in the company of mere mortals such as themselves. She had made a great show of carefully selecting which seat was least likely to suffer an Acromantula attack, spilled hot drinks or goodness knew what else, then picked at her food, loudly declaring that Mars was bright again, so it only made sense to eat a little more to gain strength for the oncoming battle.

The extra food didn't seem to do her much good. Sibyll was sitting rapt in her chair, eyes fixed straight ahead and utterly immobile. Minerva decided to make an effort to be civil.

"Sibyll, dear, do have a poached egg or two, they really are excellent."

"The Dark Lord, once beaten, now come," Trelawney declared in a harsh voice most unlike her usual misty tones.

"Yes, we know, dear. Please have an egg, you're looking awfully thin-"

"Once more for power, for blood, for none

Nine will react, and nine will return

Across the sea lest the world will churn

Magic will suffer, magic will rise

But to the stag, the storm, fire and death,

The might of darkness will meet its demise

United, as one, Olympian, eagle, lion and snake

Will decide for good or ill the magical fate."

As soon as she fell silent, Trelawney's gaze focused once more, then fell to her plate, which she'd hardly touched. She picked up a fork and enthusiastically scooped up a couple of mouthfuls of porridge, unaware of all her colleagues' gazes fixed on her. The hall was utterly silent, barring Trelawney's slurping.

After a few moments of silence, Dumbledore finally cleared his throat.

"Sibyll," he called, calm as ever. "I wonder if you would join me for a minute or two; now, if you please. We can take a stroll around the lake, it will do you some good."

Trelawney looked thoroughly taken aback, but obediently followed the headmaster as he rose and exited the Great Hall. As soon as the door clicked shut behind them, the professors erupted into animated argument. Some were surprised, others disbelieving or scornful, and precisely one was impressed.

"Do you know," Minerva McGonagall said, her gaze still fixed on the huge wooden doors. "I think we may have actually witnessed a real prophecy. And you all know how I'm the last person who would ever say that."

Filius Flitwick snorted.

"Oh please, Minerva." he squeaked disapprovingly. "Those were just melodramatics."

"I'm not sure," Professor Sinistra ventured cautiously. "I've never heard her try to attract attention by using that voice before. And what she said about Mars being bright-"

Madam Hooch chuckled.

"Really, Augusta. I respect astrology as much as anyone," her tone suggested she didn't, "and you're the most entitled here to place any importance on it, but Sibyll's ramblings about Mars were a scam, it's all she ever does. I don't think she'd even know where to find it in the sky if we asked her."

"She probably thought it would have dramatic effect if she casually mentioned it a minute before going all rigid and and predicting doom." Professor Vector put in, shaking her head and sighing. "In fact when you think about it, the only tactic she's changed in sixteen years is her tone of voice."

"Dramatic effect is one way to put it." Pomona mumbled. "We're all lucky this didn't happen in the middle of term."

"I agree." Minerva said primly. "And as much as I do not think Divination is a solid basis for information or plans, I equally disapprove of speaking ill of my colleagues." She shot a sharp look at Hooch, who shrugged.

"Well, she's not exactly making herself a difficult target, is she?"

There were mumbled assents, but Minerva's sharp eyes switched to Severus, who was still drinking coffee and had yet to say anything. Knowing him, he would immediately show his scorn if he thought Trelawney was trying to attract attention. So if his silence was anything to go by, Minerva rather thought she had at least one other person who agreed with her.

"Well," Pomona said grimly, "with that pink hypocrite, an impending Gred and Forge attack and the fate of magic in question, this is starting to sound like an interesting year."

Minerva could only reluctantly agree.

0o0o0o0o0o0

Percy was on fire when Nico found him.

It wasn't his fault. The stupid lava wall was playing up, spitting drops of liquid-hot rock on his clothes as he raced across it. He yelped as his shirt started to singe and his back started to feel like it was being poked with white-hot roller-ball pens. He scrambled up twice as fast as he usually would have and dropped to the floor, rolling around several times in the dust, while Nico stuck his hands in his pockets and grinned. Percy still wasn't used to him smiling so often.

"New look, water boy?" the son of Hades called, for once looking amused despite his whole doom-and-gloom aura.

Percy muttered a string of Greek swearwords under his breath as he got up and roughly dusted himself down.

"That's Lordwater boy to you, gothy." he replied grumpily. "And call me that again only if you really want an excuse for a fight."

"Same goes for you, but I'll keep that in mind." Nico answered easily. In the sunlight his skin was as pale as ever, but the haunted look he'd acquired in that jam-jar had disappeared entirely, and he'd put on enough weight since to differentiate him from those creepy skeletons he occasionally liked to summon. He even acted happier, which Percy was glad of. Being surrounded by his friends, sister, and people who thought he was awesome had really brought out a bit more of the light-hearted boy Percy had once known. Nico's new friend Will Solace also had had, Percy suspected, something to do with it.

"So...did you come here just to gloat, or do you actually have a reason for standing there looking gormless?"

Nico rolled his eyes.

"D'you know, very few people on this earth could get away with speaking to a prince of the Underworld like that, Jackson."

"Ooh, prince of the underworld now, are we? Do you get privileges, like good movie seats or discounts in Uncle Death's shopping mall?"

"Shut up." Nico muttered. "And actually, yes, I do have a reason. Chiron sent me to find you. He wants to see you, me and a few others at the Big House for a reason he didn't care to divulge."

Percy's heart sank. There was usually only one reason for a summons to the big House, and that was a quest. He couldn't imagine what new quest could possibly have come up after only a month since Gaea's defeat, but he couldn't help but feel it wasn't anything good. Of course, in this particular context, the word 'good' was thoroughly subjective. Quests hardly ever qualified as 'good'; more like 'exciting' or 'useful'. Maybe even 'fun'. But never 'good'. Ugh, he was starting to sound like Annabeth. Percy loved his girlfriend, but he had no wish to start sounding like he'd swallowed Daedalus' laptop.

"What for? Are you sure he didn't give any reason?"

Nico shrugged.

"Dunno, man. He really didn't give any details, but I suggest we hurry up, 'cause we're already late. You have noidea how many places someone can be when you're looking for them in this camp-"

"Fifty-two. Fifty-three, if you count the small alcove in Zeus' Fist."

Nico raised an eyebrow.

Percy shrugged.

"ADHD, remember? I bet everyone in this camp knows exactly the number of places they could hide. It's part of human survival instinct." He straightened briskly. "Could you just shadowtravel us there? Might save us some time."

Nico winced, like this was a subject that had been discussed numerous times and he was rapidly getting sick of.

"Can't." he grumbled, kicking a pebble. "Doctor's orders. Will says that if I try anything like that again for the next month I'll dissolve into a puddle of vaporous black goo."

"Aw, too bad. I have a feeling we'll get shouted at anyway, then."

Percy decided not to mention anything about Nico obeying Will's 'doctor' orders. It was extremely unusual for the son of Hades to be any kind of submissive, but the subject of Will Solace was still touchy, especially ever since Leo had said "two stubborn, scrawny gits should get into even more trouble than one", which for some reason had made Nico mad.

So for once, Percy kept his mouth shut when he was supposed to and followed Nico up the hill to the Big House. They didn't say much - both were busy wondering why they were specifically being called upon.

In the basement, the two boys found Annabeth and Frank playing rock-paper-scissors (it didn't work too well: Annabeth could tell what Frank was going to do by reading his body language) with Piper and Hazel as an audience. Jason was polishing his new glasses as he talked to Leo, who was building a submarine out of Fonzies and pipe cleaners. Percy walked over to Annabeth and wrapped an arm around her, just as Frank shouted in triumph.

"Ha! Rock! Got you!"

Annabeth rolled her eyes.

"You distracted me, Seaweed Brain."

Percy smirked.

"Just by putting my arm round you? Then what will this do?"

He leaned forward and kissed her. She poked his ribs, right where a lava-blister had developed. Percy winced.

"Never leave your side unprotected." she whispered into his ear, and kissed him back.

There was an almighty smack and everyone pivoted to see Leo face-down on the ping-pong table. He looked up and glared at Percy and Annabeth. They had a hard time not laughing, because Leo with his face covered in crumbs was only slightly less intimidating than him humming "Walking on Sunshine" while polishing Festus.

"Will you two stop that? Dude, I already have to deal with Jason and Piper going gooey-eyed several times daily. D'you know how many times I've tried to lock them in a room to let off all steam before they're allowed in public again?"

"That was you?" Piper interrupted, her voice shrill around the edges. Leo gave her a duh look.

"Can you honestly blame me?"

Piper opened her mouth to answer, but closed it again, blushing.

Frank put an arm round Hazel and grinned.

"Oh, don't you two start." Leo groaned.

Hazel smiled gently.

"Leo, I'm sure sure you'll get to see Calypso soon."

The son of Hephaestus spluttered.

"I'm not- this isn't- wait... Hang on, you can't just-"

"Zeus' firecrackers, I hope you're not going to be that lovey-dovey while I'm here. It's all so sickeningly sweet - I'm going to develop toothache." said a familiar girl's voice. The demigods whirled around as one.

Thalia Grace was leaning against the door frame, smirking.

"Thalia!" Jason whooped, engulfing his sister in a bear hug. The daughter of Zeus grinned, squeezing him back.

"Hey, little bro'," she said "Miss me?"

Jason scowled.

"You know, we're practically twins now, considering you spent most of your age difference with me as a tree."

"Ah, but once big sister, always big sister, Jason, darling." She glanced over to the others and waved. "Hey guys."

They all called out greetings, and Annabeth hugged her friend with just as much enthusiasm.

"I heard you kicked Gaea's big muddy ass," Thalia said, "Dad said that even the gods couldn't do much against her."

"It was all Leo," Piper said proudly, ruffling his black curls "he had it all figured out. He and Festus managed to lure Gaea into the air, while I... uh, sang her a lullaby, and Jason stopped her from going back down. At one point, Jason and I had to go back onto the ground, so Leo single-handedly caused this absolutely ginormous firestorm-"

"Which I couldn't have done if you hadn't charmed her into a coma." Leo mumbled.

"-and then, as an extra-special child of Hephaestus, lived to tell the tale!"

Thalia looked impressed, but Leo just looked embarrassed. And sad. No doubt the re-telling of his triumph over Gaea sharpened the pain of his failure to find Calypso, Percy thought.

"What are you doing here, Thal?" Percy asked, frowning. "Not that I'm not glad to see you, but ... aren't you supposed to be off with the Hunters of Artemis and - y'know, hunting? Preferably unfriendly monsters?"

Thalia shrugged, but her gaze saddened.

"Since Phoebe and the others were killed by Orion, there's been a considerable shift in the Huntresses' rank infrastructure." she informed them. "Lady Artemis has nominated some new officers to replace those who died, but Chiron asked to see me, so she gave me leave to come here."

"And I'm very glad you did," said another voice. Chiron the centaur/teacher/mentor/chief counsellor clip-clopped into the basement, wearing the upper half of a formal suit and the horse part of his body for once free of his TARDIS-like wheelchair. He took his position at the head of the ping pong table, looking at them all with his usual kind gaze, but there was something in his demeanour that told Percy he hadn't called them to organize a table-tennis tournament.

"Thank you all for coming so promptly, though some of you took your time", he glanced at Percy and Nico, who exchanged a told you so look, "but we are once more in a delicate situation. Rachel Dare IM'd me about an hour ago, saying that she and the harpy Ella had found a particularly interesting prophecy. Rachel says that though the voice of Delphi is gone, she still has the spirit of the oracle inside her, and she can tell that this prophecy is on the verge of coming true... if it hasn't already."

He paused and took a scroll of paper from his pocket. The demigods were silent, partly out of respect for their mentor, but mostly out of dawning dread: another prophecy meant more conflict, more danger, and more lives on the line. Were the fates so cruel as to force a new impossible quest upon them when most campers had barely recovered from the last one?

Chiron unrolled the scroll and cleared his throat before speaking.

"She read it out to me, and these are its contents.

The Dark Lord, once beaten, now come

Once more for power, for blood, for none

Nine will react, and nine will return

Across the sea lest the world will churn

Magic will suffer, magic will rise

But to the stag, the storm, fire and death,

The might of darkness will meet its demise

United, as one, Olympian, eagle, lion and snake

Will decide for good or ill the magical fate."

If the demigods had been taken aback beforehand, it was nothing compared to the utter confusion among them now. After several full seconds of total lack of noise, Annabeth spoke first.

"This Dark Lord... I've no idea who it could be - I mean, it sounds like it could be Hades." She glanced at Nico, who frowned but didn't disagree. "But the description is wrong. Once beaten, now come. That can't be him... And all this about magic - does it mean the Mist is in danger of disappearing?"

"And why did you call us, specifically?" Piper asked quietly, though her expression made it clear she feared she might already know.

Chiron sighed.

"This prophecy forces me to reveal to you what the gods would hide from you - from all demigods. They have kept it secret for decades, centuries even, because the knowledge would've destroyed any semblance of peace between nations, mortals and demigods. This secret was guarded all the more closely ever since the Second World War, which as you know involved some powerful demigods, because in those few years the world experienced a mere fraction of what it would suffer should this information be divulged."

Chiron paused. Leo's hands were tapping the table-top. Percy knew him well enough by now to know that it was Morse-code, but he had no idea what it said. Hurry the hell up, probably. If so, Percy agreed with the sentiment. The tension was rising as they all waited in utter silence for the centaur to reveal this life-changing secret.

Oblivious to the tension and growing annoyance of the assembled demigods, Chiron absently played with a stray ping-pong ball. His lined face was furrowed in worry, and his expression was somewhere else entirely.

"Ananke's spindle, I hope I'm doing the right thing..." he muttered. "But if certain of the gods found out, they would find even Tartarus too good for me."

Thalia tsked, irritated.

"Well you can't back down now, you've given most of it away." she said, crossing her arms.

Chiron nodded, sadly and slowly, as if Atlas' burden had suddenly taken up residence on his shoulders.

"I am well aware," he said gravely. "But in the millennia I have lived, I have never truly come to terms with how leadership and counselling in wartime also meant that at times, only you can make the decisions. Sometimes they are easy, other times not so. It can be a choice between the life of a loved one or that of a hundred innocent strangers. It can be having to choose whether to save a starving besieged city or preserve your own exhausted army. It can mean choosing between disease, famine or immediate death. In those cases, one can never truly make the right decision, because there is no 'right', and there is no 'wrong' to it. They're just decisions based on probability, and the answer is always to choose the option that seems slightly less destructive than the others. If there's one thing I know, it's that those choices live with you forever, and when you die, people will remember you by those decisions - whether you did the 'right' thing or not, whether you could have done any better. Whether you had any choice at all. Today, another choice has been set before me: do I tell you something that I swore to Zeus personally not to? Or do I ignore the prophecy, hoping that someone else will have heard it and will act on their own? Do I ask the gods for counsel? Do I choose the option I think best, and then hope that in the long term the gods of Olympus will recognize that it was the necessary course of action, and not a rash decision made on impulse in a moment of panic?"

He fell silent, while the demigods stared at him. For Percy's part, this was the first time he had ever heard Chiron open up so much. He loved the guy like almost like a father, or a four-legged part-horse uncle. But until that moment he had never really realized just howold Chiron was. The centaur had trained heroes, fought wars, counselled great kings - of course he felt the burden of a warrior as much as other leaders did. In that moment, Percy pitied him. He felt bad for it, because an hour ago he never would have thought anyone in their right mind could pity Chiron, but right then and there, he did. If this was the first time Chiron had shared the pain of his burden as a military decision-maker, and it sure sounded like it, then Percy couldn't imagine just how heavy that burden must have become over the centuries. At least during their quests he and his friends had had each other to help make the tough choices. But Chiron had been alone, and that prompted Percy to promise himself to stand beside his old Classics teacher and defend his case, against the entire Olympian court if need be.

Chiron placed the flat of his hands on either side of the ping-pong ball and looked at each of them briefly in the eye. Finally, he spoke up again.

"Very well. For centuries, a wizarding world has been co-existing with our own. Its magic has always hidden wizards and witches from sight, much like the Mist does for us and monsters. Magic and the Mist are two different but similarly great forces, and both are the creations of Lady Hecate. Centuries ago, the goddess created her own race of people, people who would worship her and practice magic freely and for the good of all. In the beginning, the wizarding race were a blessing to humankind. Once their training was complete, wizards spread across the world, expanding magical knowledge, power, and the greatness of what wizards could achieve in every nation. Some reached China," he glanced at Frank, "and some reached America, well before the rest of the Europeans. Mortals came to know them as shamans, because in their tribes they acted as healers, oracles and wise-men." he was looking at Piper, who had Cherokee origins, as he said this.

"But as time went by, and mortals developed rumours about what magic could do, the approach to magic and wizards changed. Those who could use and control it started to get shunned, bullied, rejected as anomalies. Because magic is transferred genetically, whole families were thus exiled from their homes and regions. Of course, they had magic, so they could survive perfectly well without home comforts, and many wizards preferred to stay apart from mortals anyway, but they met hostility nearly everywhere, and the mortal governments of the time turned to official measures against them. Many were burned, though few were actual wizards, and many were executed for crimes they either had not committed or were not rightly crimes at all.

"The persecution of her people angered Hecate. It didn't help that for the past few hundred years humans had turned towards monotheism and nearly abandoned the notion of Greek gods except in art and fairy-tales. So a few centuries ago - I am beingdeliberately vague, here, Valdez," he said dryly to Leo, who was looking a bit confused at this unanticipated history lesson. "A few centuries ago, Hecate told her people to hide. She taught them new ways of using magic to completely shield their existence from mortals, and often the trick was to hide in plain sight. Because they were tired of being constantly under suspicion, and because they owed her their powers, the wizarding folk all around the world obeyed her. Time went by as time does, and now the world thinks all they have left of wizards are rumours, cheap imitations or pure myth, which is why we have such a clear but stereotypical idea of wizards and witches. They now co-exist in our world, breathe the same air and eat much the same food, but they have their own society, their own governments, schooling systems, currencies, health systems - even sports."

"Now, you must be wondering why the gods decided to keep it secret from all demigods. Even the children of Hecate don't know of the wizarding world's existence, but...why? After all, most demigods have powers of their own, they have a connection with Hecate through their godly parent, they also have a great creation of hers protecting them from detection. These were all pointed out to Hecate when she came to Zeus to ask him for support in her decision to hide wizards from the world, but she said that the demigods' knowledge of the wizarding world's existence would do more harm than good. The powerful, more ambitious and not necessarily...ah, nice demigods would try to exploit magic and use it to their own advantage, causing huge damage on earth and possibly, she warned, to the gods themselves.

"The last bit especially convinced the gods, but even if it hadn't the Second World War certainly did. What happened in those years of wartime was in equal part due to demigod and wizard actions. Some of the mortals' leaders were very powerful demigods, whereas some wizards who turned dark operated within their own society, provoking as much damage to their world as the mortals and demigods did in ours. And all of that had happened without interaction between the two hidden communities. Can you imagine what would have happened if the Nazi demigods had gotten wind of ways to appear almost instantly on the other side of the planet? Or, for that matter, if American wizards had known sons of Poseidon could control the seas, and Zeus' children the sky?"

Chiron paused again. No-one said anything. There was no point, and besides, they were too stunned to speak.

"But those were military concerns, and in times of war. What concerned Hecate especially was normal, everyday life. Some wizards and witches are attracted to and have an unfortunate affinity with what many would call the Dark Arts. Those branches of magic delved into many different areas, including warfare, torture, and necromancy," Chiron shot a slightly apologetic glance at Nico, "but also healing, foretelling and protection - especially protection of their existence. In the dark ages, those particular brands of magic weren't considered especially dark - magic was purely a way of getting the things you needed, it didn't matter how you did it. But as the centuries turned, and the wizarding community increasingly stressed the moral use of magic, those types of magic were dubbed 'Dark', and severely frowned upon - if not banned completely. Some continued to use them, believing them to be more powerful than neutral and light magic, and that it gave them superiority over other wizards, not to mention mortals. Non-magical folk were to some wizards like rats are to humans: undesirable, pesky and thoroughly to be avoided. Over time, wizarding government systems banned the use of the Dark Arts completely; the occasional school still taught them to its students, but only the theory and always under strict regulations.

"Nevertheless, some wizards discovered a liking and ability for dark magic, and a few even succeeded in gaining enough power to challenge their government. Such was the case with Grindelwald, a wizard who turned dark and reached the peak of his power during the Second World War. He was defeated, but as so often proved before, history repeated itself. In the last fifty years, another dark wizard, more powerful than any other the world had seen before, rose to power in England and gathered armies full of magical beasts and dissatisfied magical folk who sympathized with his ideologies. Long story short, he was invincible for a time, and the atmosphere in the United Kingdom was as dark and horrible as it could get. Yet, fourteen years ago he was destroyed when his power backfired as he tried to eliminate a boy that had been prophesied to defeat him - or so everyone thought. This summer, about a month ago, this wizard returned. His name is Lord Voldemort."

Chiron fell silent. The nine demigods had yet to speak at all, and the silence stretched on for so long Percy's shell-shocked brain vaguely wondered if Kronos was up to his old tricks.

"I suppose it would be too much to hope for that this Dark dude is not, in fact, the guy from the prophecy Rachel and Ella found?" Leo asked suddenly, a pained but resigned expression on his impish features.

Annabeth shook her head.

"Oh, it's him." she said. "It's obvious. Rachel said this prophecy was already happening, or on the verge of doing so. How many dark wizards have returned in the past month?"

Leo groaned and Morse-tapped crap on the tabletop. Even Percy knew that much.

"But why hide it from us?" Percy asked. "It's not like we would declare war on wizards."

"No, but it's about containing the knowledge as much as possible. Weren't you listening? Have you forgotten Octavian?" Annabeth answered, a bit exasperated. "If news spread among demigods that a wizarding world existed and vice-versa, imagine what that would mean to the demigods and wizards who want power, war, or revenge. They would seek allies, and dabble in all sorts of magic which no-one but the gods should deal with. They'd cause so much collateral damage it would be sure to start another world war."

"Kind of like why the gods kept the Roman and Greek demigods separate for ages," Thalia remarked, examining the string of her bow distractedly. "To stop us from tearing each other apart."

"A wizarding world, though..." Annabeth murmured. "This magical force must be really powerful, maybe even more than the Mist. I mean, even knowing that it exists now doesn't make me remember anything that could have hinted at its existence. The Mist protects us as well, yeah, but it doesn't like, really hide us or anything. It just messes with mortals' minds."

"I think that may be what magic does too, actually." Hazel said thoughtfully. "Because when you think about it, how else could it work? It couldn't just make mortals not see it, that would be silly. And it doesn't sound like it makes them forget whatever they happen to see. Maybe it just...hides the wizards in plain sight, and then somehow persuades mortals that anything they do see is either unworthy of their attention, or pure hallucination."

Leo looked alarmed.

"Oi, lady - you saying we've been seeing wizarding stuff our whole lives and telling ourselves we're only imagining it?"

Piper laughed.

"Don't worry, Leo. I'm sure you don't need telling that what you see is pure fiction. What was it you said you saw yesterday, again? 'A giant seaweed monster who wants to eat me?' . Turned out it was just Blackjack who'd fallen off the dock and got tangled in a forest of kelp."

Leo blushed as the others laughed.

"Yeah, yeah..." he muttered. "But I'd like to see how you would react when a wet, slimy, shrieking thing with wings and four legs shoots out of the water and nearly runs you over."

Chiron cleared his throat.

"Uplifting as it is to see how you can take a life-changing revelation with humour," he said dryly, "perhaps we could get back on track? An immensely powerful dark wizard is planning to take over the UK, then probably Europe and the rest of the world, and all you daredevil demigods can do is make reference to ponderous, panicking pegasi!"

Leo grinned.

"Dude, you are the king of alliteration."

"Valdez! Focus!"

"I can't, I'm ADHD."

"So are we all, but we don't get distracted at every opportunity we get-"

"What has alliteration got to do with-?"

"Besides, Chiron's good, but he's not the king of alliteration. I know someone in the Apollo cabin-"

"I wouldn't know, I'm dyslexic, but-"

"We're all dyslexic, Grace."

"I'm not!" Frank said proudly.

Chiron's expression was getting stormier by the second, and his eyes flashed in a way even Zeus would be proud of. Percy sympathized. The guy had just told them one of the most closely-guarded secrets of Olympus, and here were the most powerful demigods of the century, arguing over rhetorical features.

"GUYS!" he shouted, holding both arms up. "Unless we want Lord Vol-au-vent to take over the world, we have to pay attention to our head of camp!"

"Lord Voldemort, Percy Jackson." Chiron said wearily. "But thank you for your clairvoyance."

The others quieted down a bit, and since it was clear Chiron hadn't finished his Discovery of the Century's Greatest Dangers presentation, they got ready to listen again.

"This prophecy is of utmost importance," Chiron continued. "You all heard what it said: Nine shall react-"

"And nine shall return, across the sea lest the world will churn." Annabeth completed, to nobody's surprise.

"Well we know one thing," Thalia muttered. "Whoever wrote this is not the oracle of Delphi, 'cause they suck at writing poetry."

"You think we're the nine demigods, the... 'Olympian' that the prophecy's talking about?" Annabeth asked quietly.

Chiron looked grave and didn't answer, but his silence was all they needed.

Thalia groaned.

"I was afraid you were gonna say that."

"But we've just been on a quest!" Percy protested. "You said this prophecy was utterly important or whatever, but a month ago we defeated Gaea. How much more important can this Dark guy be? Why is it demigods have to send help when wizards have always managed on their own?"

Everyone looked at him, surprised at his outburst. Percy winced.

"Look, guys. I'm sorry. I know that sounded selfish, but we've only had a month of monster and giant-free time, and we're suddenly called upon to save a world we've never even heard of!"

Nico cleared is throat.

"Actually," he sounded apologetic, "I have."

Everybody's heads swivelled to look at the son of Hades. It was like watching a vocal tennis match, and even Chiron looked stunned.

"Heard of-?"

"Yes." Nico replied. "I spent a lot of time in the Underworld, as you all know, and I noticed a few weird things no-one had ever mentioned in Greek mythology - or Roman, come to that. Like, when the shades of the dead gathered to cross the Styx, sometimes I could hear Charon asking questions to some of them, and occasionally one turned back and, somehow, walked out. Charon wouldn't tell me what that was all about, so I...er," he looked vaguely uncomfortable, "sort of ambushed a shade who turned her back on him and tried to walk out. She was a ghost and everything," he assured them, "dead, you know. But she was still quite like a living person, because she looked what she must have looked like when she died, clothes and makeup and all, only grey and... well, ghost-like. I asked her what made her think she could leave the Underworld, and she got angry, saying it was her choice to go back, that she wanted to see her family and home again."

Nico rubbed his hair, frowning. The memory must have been bringing back the sheer weirdness of the event.

"Now that I think of it, pretty much all of the shades Charon talked to like that were angry or really scared, but anyway, she got the anger prize. Shades aren't supposed to be loud, that's just the way it is, but she was yelling her her head off at me - literally, 'cause it looked like she'd been beheaded - and in the end I just let her go to save my ears. I figured she'd eventually realize she couldn't leave the Underworld then come back, and that Charon had just refused her because she didn't have an obol. So I sort of forgot about her and the few others I'd seen like that. But a few months ago, I saw the same thing again, and I asked Charon if he ever saw those dead people again. He said no, and I could tell he wasn't going to tell me any more about it, but one of the shades he'd spoken to started asking me all sorts of questions. Why was I still alive, was this really the world of the dead, was he dead, etc... I told him it was, and that yes he was, and he just lost it, ranting on about how he was a great lord when he was alive and how he deserved better than this. I let him talk," Nico admitted with a shrug, "because it was a way of finding out whatever Charon wasn't telling me, and he was just spouting the most ridiculous things I'd ever heard of - like how a spell had backfired and killed him, but he'd used it for years and never hurt anyone, that it must have been his wand that went faulty..."

Chiron was utterly still, staring at Nico so blankly Percy wondered if he'd been anywhere near Medusa's head lately.

Nico looked uncomfortable again.

"I, er...didn't think he was entirely sane, so I just left him there to deal with it - after all, everyone does - and kinda forgot about it all again. Even a son of Hades shouldn't know everything about the Underworld, it's only fair in a way. But now," Nico concluded, "I think back and realize that he must have been a wizard, that all those angry or scared shades must've been magical, because they were just so much more substantial than regular ghosts, and quite frankly bizarre. There was no way they were ordinary mortals. Even dead demigods don't look and act like they did. Which means," he said more seriously, "that wizards must have a different concept of death. Those shades who decided to walk out of the Underworld - and succeeded, for all we know - chose to come back to the world of the living as ghosts. I'm sure of it. And that puts this whole prophecy thing in a different perspective, because-"

"Because this Lord Voldemort was destroyed fourteen years ago, but you've never felt his death, have you?" Annabeth said, paling slightly.

Nico nodded.

"I never knew wizards existed," Nico said, looking at Chiron, who was still impersonating the Athena Parthenos in its immobility. "But a dark lord, especially one as powerful as you say, would have had some sort of effect on me, and Bianca. We were both really young and stuck in that casino when it happened, but even then I remember we sometimes felt twinges that we later realized were signs that someone important or close to us had died." He fidgeted with the Stygian iron blade at his side. "I'm not saying this Voldemort was close to me or anything, but that much power snuffing out just does not go unnoticed in the Underworld, nor by its children. He didn't die, but by all laws of nature and probably magic, he should have. Guys," he said, looking at them all in turn, "we're somehow looking at an immortal human."

Thalia snorted, sounding disbelieving even after Nico's unexpected anecdote.

"An immortal human?" she said. "Whoever heard of such a thing? You can only be immortal if born some sort of nature spirit or made so by the gods."

"Which is why," Chiron finally joined in, "we must ask ourselves, can the wizarding world truly defeat this Dark Lord by itself? Will the demigods, who have extensive experience in fighting both monsters and immortals, leave them to this fate? And if wizards cannot prove up to the task, must we wait until Lord Voldemort gains his full strength and then proceeds to take over the international wizarding worlds, while we stay here, climbing the lava wall and living in the muted fear that one day Voldemort may discover the existence of demigods and Olympus?"

Once again, silence descended as the demigods took this in. Chiron always had a way of rationalizing things. Usually, that skill made things clearer and more straightforward to decide upon, but this time it only opened a hundred other doors, each filled with so many questions and 'if' situations that the whole Gaea affair seemed quite familiar in its way. After all, they had known exactly who she was, what she was, who her main agents were, some elements of her complicated plans - and especially, they'd had occasional help from the gods and other anti-Gaea immortals.

This was exactly what Annabeth pointed out to Chiron.

"So in effect, you'd be sending us into a desert with a toothbrush each and a towel to share." she said.

Jason grinned.

"Well, to be fair, if he did do that, Percy could summon up water, Nico could provide shade, Thalia could hunt us some snakes to eat, and I could make a breeze. Frank and Hazel would be perfect bodyguards too, and Leo and Annabeth together could figure out a machine out of there in about an hour."

"Let's please not give the gods any ideas, though." Percy mumbled, thinking of Tartarus. "I've had enough of waterless wastelands for a lifetime. Two lifetimes. No, ten."

"We have literally no idea what this wizarding world is like, how it works, how we would fit in if at all, and how real wizards would receive us." Annabeth went on, ignoring them.

Piper slapped her forehead, as though she'd had a brainwave.

"I don't even know why we're discussing this!" she cried. "How on earth are we supposed to help the wizards defeat Voldemort while trying to keep a low profile when we're not wizards ourselves? It'd be like trying to attack Persephone in her own palace while pretending to be dead like all her other servants!"

"This may sound uncooperative, but that has actually been attempted," Frank mumbled.

"Not helping, Zhang!"

"Sorry."

Hazel huffed.

"Don't apologize, Frank. Actually, I can't believe we're discussing this so much either, but for entirely different reasons. There has been a prophecy," she pointed out clearly. "That means it cannot be ignored, nor changed, nor interpreted too hastily. If we are the nine demigods it's talking about, then we have no choice. We've got to help the wizards."

"You're only saying that because you sympathize with other people who have magic," Leo said, frowning. "I mean, you use the Mist and all, but it's still a super-mysterious creation of Hecate's."

Hazel looked slightly hurt.

"Leo, I think we should help because it's our duty as much as a matter of compassion!"

"Spoken like a Roman." Thalia said gloomily, picking at her nails, painted black and silver that day.

"What's wrong with Roman?" Franks asked testily.

"Nothing. Except you tend to confuse duty and moral obligation. Loyalty and stupidity. Not to mention orders and friendly advice. That sort of thing."

Hazel was fuming and about to retort sharply, but Annabeth stepped in hastily with her hands held out for peace.

"Guys, please don't destroy in one afternoon what we fought to achieve for over a year."

Hazel grudgingly remained silent, while Frank looped an arm around her, glaring at Thalia, who shrugged and made an It's true, mate gesture.

Chiron heaved a long-suffering sigh and rubbed his temples.

"Going back to Piper's earlier point," he said tiredly. "Yes, it's true you're not wizards, but you're not the only ones aware of the prophecy so far. Rachel told me as soon as she realized it was important, but Ella doesn't know anything of its significance, so I contacted the gods of Olympus. They urge us to take the decision for ourselves, but insisted Hecate should help, since it was her world in danger. The goddess has agreed to bless you with the gift of magic should you decide to help. You would retain your original powers, of course, but you would also be able to use magic in the same way as wizards."

Piper looked like she was dying to say something, so Chiron gestured for her to speak.

"But how, exactly, are we going to help?" she asked. "We can't just get there on the Argo II and hang out until Lord Voldemort launches an attack. We'd be seen. We'd be questioned. It's way too risky."

"Says the girl who participated in some of the riskiest things in history since Zeus discovered lightning bolts." Jason muttered under his breath. Piper elbowed him in the ribs.

"I was getting to that." Chiron replied. "Despite the utter secrecy around the matter, some people, including myself, have knowledge of the wizarding world. These are few and far between, but we do keep tabs on some aspects of it. The initial rise of Voldemort we followed closely, for instance. We learned that the boy Voldemort tried to destroy after murdering his parents all those years ago is still alive. He's currently studying at the best school of magic in the world, Hogwarts."

Leo sniggered. Everyone else looked at him blankly.

"Oh, come on," he said, still laughing. "Get it, anyone? Hogwarts? Like a pig's skin condition?" He laughed again, clearly finding the name hilarious. Percy would have as well, but Annabeth was giving him the don't you dare glare.

Piper raised an eyebrow.

"Leo Valdez, you are so immature." she said loftily.

"Lady, I invented immature! Girls luuurve immature! I'm so immature they always want to kiss me and call me babe!"

"Watch out, or I'll do just that." Thalia said darkly. "And you should know, among the huntresses, a 'kiss' means something to do with these lovely, sharp, knives." She held up her dagger, her eyes glinting.

Leo gulped.

"I'm...all right, thanks. Keep your kisses, I'll manage."

"Yes, getting back to Hogwarts," Chiron said hurriedly before Thalia could retort, "the boy's name is Harry Potter. The entire future of the wizarding world depends on him. If you were to help the wizards, your first and foremost task would be to attend Hogwarts and protect him from any harm. The headmaster at Hogwarts is reportedly the best and wisest wizard in the world. Persuade him to give you a place in the school - Miss McLean, I believe your powers will be most useful if he proves difficult to convince - and attend classes, study and make friends like you would in any school."

"So not much, then." Percy joked, but his brain was racing. This Harry Potter kid, the key to saving the wizarding world? "So... we'd just be really elaborate bodyguards?"

Annabeth smirked.

"Don't sound so disappointed, Seaweed Brain. The fate of the world can't always depend on you or Jason."

"I'm not disappointed!" he protested. "If anything I'm relieved, but I don't understand-"

"Story of my life, yours, and everyone else's in this room." Nico commented idly.

"-I don't understand why so many of us have to protect this Potter kid when we should be... I dunno, fighting Voldemort's minions or something. Nine demigod bodyguards seems a bit much, especially if he survived a murder attack by the darkest lunatic in history when he was, like, tiny."

Chiron nodded.

"I agree, Percy, but the situation is almost entirely different now. Voldemort has returned - that is a fact, not a possibility - stronger and better prepared than before. He used dark magic and an even darker spell to regain his body, absorbing some of the boy's blood as insurance. His past weakness has become his strength. There is next to no safety left for Harry Potter, because while the boy lives, so does Voldemort, yet he is a constant threat to the Dark Lord, because of his special connection to him."

"Connection?" Percy asked, frowning. "They're related?"

Chiron waved a hand around impatiently.

"Everyone is more or less related in the wizarding world-" ("Ew," muttered Thalia, forgetting her own origins.) "-but Harry Potter has a special connection with Voldemort because the boy absorbed some of his powers when he was destroyed. Don't ask, I have no idea how. Ask the lady Hecate if you see her. But the point is, their minds are connected, a bit like-"

"A bit like the empathy link between me and Grover?" Percy guessed.

Chiron hesitated.

"In the vaguest possible way, yes, but-"

"Like me and Gaea, then." Leo suggested. "I witnessed her murder my mom, and during this whole Great Prophecy Quest thing it was me she often looked for in the first few months."

"And you defeated her in the end," Piper said, smiling a bit. "Dare I hope that could be a good omen for the wizarding world?"

"Yes, yes, if you like, similar to Leo and Gaea. But as I was saying," Chiron pressed on, "the point is that their minds are connected: sometimes Harry gets flashes of Voldemort's moods or thoughts. It's only a matter of time before the Dark Lord realizes what's happening, and when he does, Harry will be in even greater danger. His safety is essential," Chiron slapped the table for emphasis, "in ensuring any positive future for the wizarding world."

"Gh." said Thalia, tilting her head back until it butted against the wall. She sounded resigned. "So we don't really have a choice in the matter. Hazel's right: we can't ignore it, and if we somehow do, we'll never forgive ourselves."

"There is always a choice." Chiron said gravely. "And in this case, the choice is yours. My role was to guide you and give you an explanation. You all know the facts. Choose. But one things must be stressed," he warned, eyeing each of them in turn, "nine must go, or nine must stay. You are the nine, that much is clear. If but one of you chooses not to aid the wizarding world, the other eight cannot go alone."

"Eight is hardly alone." Leo muttered, crossing his arms, but no-one argued with the old centaur.

As for Percy, he was going through he same agonizing choice as the others. Study with Annabeth in New York, or fight and risk your life again? Help thousands of innocent people he'd never met in a country he'd never been to, or stay and protect his home? Get bored in maths, or get bored in astronomy or whatever they taught at Hogwarts? Help Harry Potter, the light of the wizarding world, or make daisy chains with dryads?

He looked at Annabeth. She had that look he knew so well and loved. As long as we're together, it said, we can do anything.

Percy shrugged, then nonchalantly grinned and put an arm around her waist.

"Well, I don't know about you guys," he said, "but we're in!"

Piper and Jason exchanged one final look and nodded as one.

"Count us in, too."

Hazel and Frank smiled slightly, holding hands.

"You're not going anywhere without us," Hazel said sweetly.

Leo whooped and punched the air.

"Yeah! Let's kick some Dark Lord butt! Team Leo is IN, baby!"

Nico and Thalia rolled their eyes, then looked at each other.

"Well," Nico said finally, "If Camp Half-Blood is my home now, and this Dark Lord is threatening it even partially, I'm going as well. Besides," he added, his dark eyes glittering dangerously. "I want to meet the guy who managed to escape my dad."

Thalia smirked.

"And I'm not letting my baby brother getting all the glory again." she declared.

Chiron's mouth stretched into a wide smile, and his chest puffed out with pride.

"I never doubted any of you!" he said. "I realize that you need rest and time to recover from last month's quest, but prophecies always have a knack of arriving at exactly the wrong time."

"Or the right time, depending on how you look at it." Hazel remarked. "Rachel did discover it just in time to warn us, didn't she? Summer's nearly over."

"Quite. And as for rest, I wouldn't worry. Despite being all about magic, Hogwarts is first and foremost a school. Attending classes will be fruitcake compared to what you've all had to deal with lately."

Percy groaned.

"Oh, man, I'd forgotten about that. How are we supposed to study magic if we know strictly nothing about it?"

"We'll do what every person does when they breach a new subject, Percy." Annabeth said calmly. "We'll study."

"How? We can barely read in English." Percy grumbled.

"We'll manage." She squeezed his hand reassuringly, and Percy felt slightly embarrassed that, of all things, studying was the thing he was worrying about at the moment.

"The goddess Hecate will provide means of transport for you to reach Hogwarts," Chiron said, back to business. "Once there, ask to see the headmaster, then somehow convince him to take you in. Locate Harry Potter and protect him at all costs. Any signs of activity from Voldemort, report to me. I will give you enough drachmas for you to IM the camp as often as you like, and if there are any signs of a battle, contact us before anything else. Some of the gods know what you are going through, and will deal with any issues you report back to them quickly and discreetly."

Percy grinned.

"The gods? Discreet? That I have yet to see."

Annabeth nudged him.

"Careful." she muttered.

"What? It's a compliment!"

"Well, don't shout it any louder, 'cause the gods will take it as a challenge, dude." Leo says wisely. "It's like when Piper once said Well, at least we're safe, aren't we? Then thwack, Sciron's arrow nearly impales her braids."

Piper flapped her hands around. "Don't!" she cried. "I keep wanting to bury my head in the sand every time I think of that!"

"While you are in the wizarding world, you must be on your guard at all times," Chiron warned. "You cannot afford to make mistakes - one of them could result in the harm or death of Harry Potter. You must ally yourselves to him. Befriend him, but don't get too close: blowing your cover would be the most disastrous thing that could happen. Is that clear?"

They all nodded, but Leo cleared his throat.

"Wouldn't that be the death of Harry Potter? The most disastrous thing that could happen, I mean."

Chiron shook his head slightly.

"As important as his safety is, that is primarily the headmaster's responsibility, and Harry's own. You must guard him, yes, but only so far as you can. Do not make it obvious you are protecting him, stay at a distance. Befriend his friends, make allies of them. Get to know his enemies if he has any at school, make arrangements with them. Who knows? Maybe even turn their relations to your advantage. You are all old enough and certainly experienced enough to know the importance of reliable allies and sound deals. I am in part entrusting you with the safety of Harry Potter, but I am also setting you the task of establishing a net of spies, informers, friends and reinforcements. You will no doubt meet relatives of Ancient Greece and Rome creatures - see if they can be of any help. Use your demigod powers as much as you like, but - and this goes without saying - never make them obvious. Keep a low profile."

Chiron looked as grave as ever.

"War is coming. That also is clear. Lord Voldemort will not be defeated without battles on a large scale. You must prepare your surroundings as well as yourselves. Learn to defend yourselves using magic as well as practising your regular powers - take full advantage of the excellent education you will get be getting at Hogwarts."

The nine demigods glanced around at each other, some gulping, others unnerved at this new and highly strategic approach to war. Thalia, Nico and Frank looked impassive, but Percy knew them well enough to know that they too were aware of the magnitude of the task set to them.

"Well, I've always wanted to be a spy." Leo said after a few moments, grinning. "Guess throwing us in the deep is the only way we'll learn, isn't it?"

Percy snorted. "That's one way to put it. But guys, this is huge. It's not a quest, it's a real, top-secret mission. This time, we won't have someone or something to look for and bring back – and we certainly won't have as much help as we've had during quests so far. This… we're not prepared for this; it's like the Ancient Greek version of the CIA."

Annabeth's eyebrows rose.

"Percy Jackson, taking something seriously from the beginning? Well, now I've seen everything."

"Ah, don't worry guys." Jason said shrugging, his mouth stretching into a smile. "We can deal with the difficulties as they come; for now, all we need to do is concentrate on the first thing: infiltrate Hogwarts. And I have yet to see a day when the nine of us together have failed to achieve what we wanted."

Hazel nodded. "He's right." She said solemnly, holding Frank's hand. "We were the Seven of the Great Prophecy, and Thalia and Nico are children of the Zeus and Hades. Together, there's nothing we can't do."

Nico winced slightly at her words. Thalia noticed.

"Don't worry, Nico. What Hazel's trying to say is that no matter what, we have each other's back. We're all allowed to be something of a loner," she said, smiling in a way that contrasted greatly with her usual tough attitude, "but only as long as someone's there to pull us out of trouble."

Chiron was looking proudly at them all.

"It gladdens an old centaur's heart to see such solidarity," he declared. "This is what camp Half-Blood was founded for. It is a haven to permit demigods to train to be heroes, certainly, but also to form ties of friendship stronger than magic, longer-lasting than life, and deeper than the roots of Gaea. It saddens me to know how, but I believe that through your individual adventures you have already discovered how the true keys to success are trust, and friendship. Without them, there are no alliances, no victories, nothing to be gained."

Hazel, Annabeth and Piper, best friends since the whole Gaea business, looked at each other knowingly. The three were virtually inseparable now, and Percy knew their ties of friendship reached further than he, ignorant male that he was, could ever fathom. Much of it, he knew, was due to their occasionally unsettling ability to communicate with looks and tiny signals alone. Such attempts made between Percy, Jason, Frank or the others floundered completely unless one of the girls was there to translate. Percy was getting slightly better at interpreting Annabeth's body language, but he had seen entirely non-verbal conversations between her and Piper that had often ended up with the two girls working in harmony, and a very confused Percy. He sighed a bit wistfully. It'd be great to have communication skills similar to those of girls – very useful for battlefields and arguments.

"That's settled, then." Percy said. "So. How are we getting to Hogwarts?"