The odd group was clustered around a cosy little campfire. The girl had mousy brown hair and a brown dress and completed the look with a scarf on her head. She was busy poking around the fire and tending to it.

The only reason why Percy did not tense up was because Harry was relaxed around the newcomer. The boy himself was nursing a tea cup, and Percy snorted, "Really dude? Tea? You couldn't be any more British if you tried."

Harry shot him a two-fingered salute, only for the girl to look at him reproachfully and he sheepishly apologised. Meanwhile, Nico bowed to the lady, "Hello again, Lady Hestia."

Percy vaguely recognised the name and decided to do the smart thing, he knelt and bowed. The now-named Hestia studied him, her red eyes locked onto him. Then she spoke. "Sit, Percy Jackson. Would you like some dinner?"

The girl snapped her fingers. Immediately, a bizarre-looking humanoid popped into existence. Harry blurted, "Dobby! What are you doing here?"

Dobby flapped his long ears, "Mr Harry Potter! I being helping my Lady Hestia!"

Hestia cleared her throat and gently chided, "Dobby… It is 'I am helping'."

She smiled at the House Elf, "Don't worry, your English is improving."

Dobby looked bashful, "I am sorry Mistress of the Hearth. I shall get back to dinner."

He snapped his fingers and a picnic appeared at the edge of the fire. There were plates of roast beef, baked potatoes, buttered carrots, fresh bread and more, enough for a feast. There was even a two-meter-long dog biscuit for Mrs O' Leary. The boys scraped a part of their meal into the fire and intoned, "For the Gods!"

Hestia smiled approvingly, "Thank you. As tender of the flame, I get a share of every sacrifice, you know."

Something clicked for Percy, "I recognize you now. The first time I came to camp, you were sitting by the fire, in the middle of the commons area."

She smiled wryly, "Indeed… Alas, you did not stop to talk. Don't worry, that isn't inherently a bad thing. Most demigods never do. Nico often talks to me, and Harry does too. Most other demigods simply rush about. No time for visiting family."

Harry asked, "Milady? How do you know Dobby the House Elf?"

Hestia smiled, "Now that… Is an interesting story. When Hecate first created the Wizarding world, she wanted them to have some companions to help them lead an easier life. She approached me, and together we created the race of House Elves. One of my domains is the Home, and House Elves were created to look after the household. Sadly, over the centuries, Wizardkind have been taking them for granted. Take Dobby for example… His former master, Lucius Malfoy, was abusive towards him. Which is why I am grateful to you, Harry, for liberating him and taking him into your own employ."

She continued, "I also appreciate your godfather Sirius Black from dissuading your friend, Hermione's crusade to free the House Elves. You see, as I said before, House Elves were created to take care of the home, thus they have an inbuilt desire to take care of a place they call home. 'Freeing' them would be anathema for them. Though the practice of giving them clothes doesn't free them from service entirely. Instead, it allows them to seek out another place where their services may be more appreciated, or they return to me."

Nico asked, "My lady, why aren't you with the other Olympians fighting Typhon?"

She shrugged, "I'm not much for fighting. Besides, someone has to keep the home fires burning while the other gods are away."

Percy chipped in, "So you're guarding Mount Olympus?"

Hestia let out a slow breath, "'Guard' may be too strong a word. But if you ever need a warm place to sit and a home-cooked meal, you are welcome to visit. Now, please eat. Dobby has worked hard for it and I am not overly fond of seeing his work go unappreciated."

The boys finished their meal fairly quickly before she spoke again, "I take it, you had a good visit with May Castellan? I understand that you have questions. You see, she was born with a gift. She could see through the Mist."

Percy stirred a little, "Like my mother! But the glowing-eyes thing –"

Hestia's face turned sad, "Some bear the curse of sight better than others. For a while, May Castellan had many talents. She attracted the attention of Hermes himself. They had a beautiful baby boy. For a brief time, she was happy. But then she went too far. This is a story I do not tell too often. But May Castellan saw too much. If you are to understand your enemy Luke, you must understand his family."

Percy whistled softly, "No wonder Luke ran away. I mean, it wasn't right to leave his mom like that, but still - he was just a kid. Hermes shouldn't have abandoned them."

The goddess smiled sadly, "It's easy to judge others."

She sternly warned, "But will you follow Luke's path? Seek the same powers?'

Nico set down his plate. "We have no choice, my lady. It's the only way Percy stands a chance."

For a while, she said nothing. Then she opened her hand and the fire roared. Flames shot ten metres into the air before dying back down to normal. She lightly said, "Not all powers are spectacular Sometimes the hardest power to master is the power of yielding. Do you believe me?"

Harry and Percy nodded, a little intimidated, and she smiled, "You are a good hero, Percy Jackson. Not too proud. I like that. But you have much to learn. When Dionysus was made a god, I gave up my throne for him. It was the only way to avoid a civil war among the gods."

Harry reminisced a lesson from Zoe, all those years ago. He spoke, "It unbalanced the council. Suddenly there were seven gods and five goddesses.'

Hestia shrugged. "It was the best solution, not a perfect one. Now I tend the fire. I fade slowly into the background. No one will ever write epic poems about the deeds of Hestia. But that is no matter. I keep the peace. I yield when necessary. Can you do this?'

She eyed Percy carefully. "Will you continue your quest?"

He asked, "Are you planning to dissuade me from going through with this plan?"

She shook her head, "I am here because when all else fails, when all the other mighty gods have gone off to war, I am all that's left. Home. Hearth. I am the last Olympian. Please remember me when you face your final decision."

Percy thought about it and then shook his head, "I have to continue, my lady. I have to stop Luke – I mean Kronos."

Hestia nodded. "Very well. I cannot be of much assistance, beyond what I have already told you. But since you sacrificed to me, I can return you to your own hearth. I will see you again, Percy, on Olympus."

She waved her hand, and the next thing that anyone knew, they were all at Sally Jackson's apartment.

The bad news was that Mrs O' Leary was sent with them. Fortunately, Remus was home and he quickly enlarged the room to accommodate her.

Remus Lupin quickly hugged the boys before they convened in the living room. He spoke up, "So I just spoke to Tonks. Remember in your Fourth Year, she was pregnant? She and her baby, Teddy Blofis are fine, along with her husband Paul. They're planning to visit us soon."

Harry shook his head, "Uncle Remus? Now's really not a good time. A war is about to break."

His face grew serious, "Anything we can do to help?"

Harry continued, "Well, mother Artemis and the other gods have gone to slow down the Titan, Typhon. Also, Nico has a really risky plan."

Percy filled them in, and Sally looked worried, "Percy, it's dangerous. Even for you."

Nico softly spoke, "Mrs Jackson, Percy needs your blessing. The process has to start that way. I wasn't sure until we met Luke's mom, but now I'm positive. This has only been done successfully twice before. Both times, the mother had to give her blessing. She had to be willing to let her child take the risk.'

Percy implored, "Mom, I can't do this without you."

Harry grasped Percy's shoulder, "Mrs Jackson. I promise you, I won't let him die. He's one of my best friends."

She thought about it for a long time, and then she breathed out, "Percy, I give you my blessing."

No sooner had she done so, when Nico stood up, "Percy… It's time."

Just before they left, Sally called out, "One last thing. If you – if you survive this fight with Kronos, send me a sign."

Remus also said, "Harry… James and Lily would probably haunt me for this, but, I know I can't stop you. I'll do my best to help out. After your task, meet us at Grimmauld Place. I shall speak to Dumbledore and gather the 'old crowd'."

The two boys nodded firmly and Percy said, "Don't worry, it won't end up like it did for Theseus."

Remus tilted his head curiously, "Theseus? The only Theseus I know is Theseus Scamander."

Harry explained, "Theseus was a Greek hero. He was supposed to raise white sails when he came home to Athens. Except he forgot. And his father jumped off the palace roof in despair."

Percy promised with a weak grin, "Don't worry mom, it'll be something blue."

After some last goodbyes, Harry, Nico, Percy and Mrs O' Leary Shadow-Travelled away. They emerged in Central Park, a little disoriented. When they recovered, Nico headed towards a cluster of boulders. He explained, "The Underworld has two major entrances. You know the one in L.A, which is Charon's ferry. Most souls go that way, but there's a smaller path, harder to find. The Door of Orpheus."

Harry spoke up, "He was the bloke with the lyre, right?"

Nico nodded, "He used his music to charm the earth and open a new path into the Underworld. He sang his way right into Hades' palace and almost got away with his wife's soul."

Percy stuffed his hands in his pockets, "So, how do we get it open?"

"We need music", came the reply.

Harry raised a hand, "I think I know a Charm that can play music."

However, Percy grinned, "I have a better idea. My empathy link's been feeling something for the past few minutes."

Harry caught on, "Blimey! Grover!"

Then Percy closed his eyes and concentrated. Nothing happened for a while, and then Percy opened his eyes and stumbled. Harry steadied him, "You alright?"

The son of Poseidon regained his balance, "I… yeah, I got through. He's on his way."

A minute later, a familiar satyr came tumbling out of the trees and fell flat on his noggin. Harry laughed and helped him up, "You okay, Grover?"

The satyr grumbled, "Oh, I'm fine. I was at the other end of the park. The dryads had this great idea of passing me through the trees to get me here. They don't understand height very well."

When he stood, Harry got a good look at him. As it turned out, Grover had decided to ditch his fake feet and walk around with his hooves showing. His horns were also growing bigger and poked out from his curly hair.

Then Percy spoke to him, "Where have you been, man? We haven't seen you in a month!"

Grover's grin melted and his face had a look of confusion, "A month? Hold up… What month is it?"

Percy replied, "July."

At that, the colour on his face drained, "That's impossible. It's June. I just lay down to take a nap and – wait! I remember now! He knocked me out. Percy, we have to stop him!"

Percy grabbed the panicked goat-man, "Whoa! Dude! Slow down. Tell me what happened."

He took a deep breath, "I was … I was walking in the woods up by Harlem Meer. And I felt this tremble in the ground, like something powerful was near. Since Pan's death, I can feel when something is wrong in nature. It's like my ears and eyes are sharper when I'm in the wild. Anyway, I started following the scent. This man in a long black coat was walking through the park, and I noticed he didn't cast a shadow. Middle of a sunny day, and he cast no shadow. He kind of shimmered as he moved. And whenever he passed humans, they would pass out or curl up and go to sleep. After he left, they got up and walked about like nothing happened."

Nico leaned in closer, "Grover? What happened next?"

He gulped, "I followed the guy. He kept looking up at the buildings around the park like he was making estimates or something. This jogger ran by, and she curled up on the sidewalk and started snoring. He put his hand on her forehead like he was checking her temperature. Then he kept walking. By this time, I knew he was a monster or something even worse. I followed him into this grove, to the base of a big elm tree. I was about to summon some dryads to help me capture him when he turned and –"

Grover swallowed, "I-I couldn't make out his face because it kept shifting. Just looking at him made me sleepy. I asked him what he was doing and he said, 'Just having a look around. You should always scout a battlefield before the battle'. I told him that the forest is under my protection. He laughed and said, 'You're lucky I'm saving my energy for the main event, little satyr. I'll just grant you a short nap. Pleasant dreams'. And that's the last thing I remember."

Nico whistled slowly, "Grover, you just met Morpheus, the god of dreams. You're lucky you ever woke up! He's working for Kronos. We know that already. A lot of the minor gods are. This just proves there's going to be an invasion. Percy, we have to get on with our plan."

At Grover's confusion, they explained it, and he suppressed a shiver. Percy told him, "I'm not asking you to come, man. I know you just woke up. But we need some music to open the door. Can you do it?"

Grover inhaled and exhaled a few times before raising his reed pipes to his lips. As he played the boulders trembled and cracked open, revealing a triangular crevice. Before they ventured down, Grover asked, "Anything I can do?"

Harry told him, "Why don't you rally the nature spirits. Also, tell Juniper that you're okay. We'll take it from here."

He hugged the three boys, "Be careful down there! Come back alive!"

The boys entered the crevice and down a set of stairs that seemed to go on forever. They were all silent, the only noisy one was the lone female with them, gambolling about. About an hour later, a new sound reached their ears, a roar of a river.

The steps dumped the trio at the base of a cliff, on a plain of black volcanic sand. To the right, the River Styx gushed from the rocks and roared off in a cascade of rapids. On the left, far away in the gloom, fires burned on the ramparts of Erebos, the great black walls of Hades' kingdom.

The River Styx's current swirled with strange objects – broken toys, ripped-up college diplomas, wilted homecoming corsages – all the dreams people had thrown away as they'd passed from life into death. Percy joked, "So… What now? Dive right in?"

Nico shot him a look, "Don't be daft! You have to prepare yourself first. Otherwise the river will destroy you. It will burn away your body and soul. There is only one way to stay anchored to your mortal life. You have to …"

Whatever he was about to say next, died in his throat. He glanced behind Percy and Harry, and his eyes widened. They turned to face with the ghost of a Greek warrior. The warrior was tall, buff, a scarred face and closely shaved black hair. He wore a white tunic and bronze armour and held a plumed war helm under his arm. However, his eyes were human – pale green like a shallow sea – and a bloody arrow stuck out of his left calf, just above the ankle.

You didn't need to be a Greek historian to know who was in front of them.

Percy breathed, "Achilles."

The ghost nodded, "I warned the other one not to follow my path. Now I will warn you. Do not do this. It will make you powerful. But it will also make you weak. Your prowess in combat will be beyond any mortal, but your weaknesses, your failings will increase as well."

His gazed moved to his bloody foot, "This is only my physical weakness, demigod. My mother, Thetis, held me there when she dipped me in the Styx. What really killed me was my own arrogance. Beware! Turn back!"

It suddenly struck Percy, as to why Luke was able to host Kronos. Without this ritual, his body would have disintegrated. Luke bathed in the River Styx and was now invincible. With that thought in mind, Percy's mind was now made up, "I have to. Otherwise I don't stand a chance."

Achilles lowered his head, " Let the gods witness I tried. Hero, if you must do this, concentrate on your mortal point. Imagine one spot of your body that will remain vulnerable. This is the point where your soul will anchor your body to the world. It will be your greatest weakness, but also your only hope. No man may be completely invulnerable. Lose sight of what keeps you mortal, and the River Styx will burn you to ashes. You will cease to exist."

Percy resisted the urge to ask where Luke's weak spot was, but didn't want to piss off, arguably the greatest demigod in Greek history. Achilles then vanished with a final warning. Harry and Nico waited while Percy gathered his thoughts and psyched himself up. Finally, he stepped into the river, as Harry and Nico waited patiently.

As they waited, Nico turned to Harry, "You know, I was going to offer you the same thing. Just to give us an extra edge in the war."

Harry snorted a little, "Honestly… I was a little tempted, but I wasn't sure if I could find a spot on my body that could serve as a vulnerable spot. Also, I'm not sure if either of my mums would have approved of this stunt."

Just then, Percy Jackson burst out of the river, and he was a mess. He staggered onto the sandy shore and his arms were bright red, whether through burns or blood, Harry wasn't sure. Percy looked around for a few moments before he lay down and let himself recover.

Nico hesitantly asked, "Do you feel… Stronger?"

Now healed, Percy shrugged, "I don't feel any different?"

Harry began unsheathing his sword, but Percy cut him off, "Let's not give it a test run, dude."

Harry pouted a little before sheathing it once again, "Let's get out of here. We've got a war to prepare for. Before we go, though, Nico I heard from Bianca that your dad is not helping the other gods stop Typhon."

He nodded, "Yeah, she's gone to try and convince him. Now that we're done here, I'm going to go join her."

He Shadow-Travelled away, before Harry and Percy climbed aboard Mrs O' Leary and they Shadow-Travelled away as well. They were back in Central Park when Percy dismounted. He looked up at Harry, who was still on top of the sleepy hellhound, "You coming? We're going to rendezvous with Annabeth at Queens Midtown Tunnel."

Harry shook his head, "You go ahead. I'll meet you there. I got to go check on the reinforcements. We're going to need all the help we can get. I'm meeting with uncle Sirius and Remus as they gather the 'old crowd'. Oh, and think fast!"

He tossed a compact mirror at Percy, who somehow caught it. Harry called out, "I have another pair, just say my name to the mirror and ask to contact me. My dad invented these with Sirius, Remus, and Peter Pettigrew. They are communication mirrors, way easier than Iris Messaging, Annabeth has them too, and they are unbreakable."

Percy began sprinting away, leaving Harry and Mrs O' Leary in Central Park. The son of Poseidon took out his mirror and called her. When she picked up, she yelled, "Percy, where have you been! We've been worried sick! We're on our way, almost to the Queens Midtown Tunnel, like we decided earlier. But, Percy, what are you planning? We've left the camp virtually undefended and there's no way the gods –"

He interrupted her, "Trust me, I'll see you there. I spoke to Harry too. He's off to get some reinforcements. I'm assuming he means the Hunters. Though he was also meeting with his uncles first, for something."

Around late afternoon, a taxi that he hailed, dropped him to the Empire State Building. He didn't have to wait long, as three white vans pulled up. Each of them had a logo that read, 'Delphi Strawberry Service'. Argus drove one van, while two harpies were piloting the other two vans. Annabeth and a bunch of other demigods poured out, and even Chiron showed up. A notable absence was the Ares Cabin, who were clearly still sulking. In all, they had a force of 70-strong campers.

He turned to the group, "Thanks for coming, everybody. Chiron, after you."

The centaur shook his head, "This is as far as I will go, Percy. I merely came to wish you luck, my boy. But I make it a point never to visit Olympus unless I am summoned."

Percy protested, "But you're our leader."

He smiled, 'You flatter me, but I am your trainer, your teacher. That is not the same as being your leader. I will go gather what allies I can. It may not be too late to convince my centaur brethren to help. I'm sure my British cousins will be up for the battle. Meanwhile, you called the campers here, Percy. You are the leader."

Safe to say, Percy was looking uncomfortable with all the attention. Everybody was looking at him expectantly, even Annabeth. He breathed in slowly and exhaled, "Right… So like I told Annabeth over the mirror, something bad is going to happen by tonight. Some kind of trap. We've got to help defend the city. Maybe some of the Gods are still on Mount Olympus."

Back with Harry, Mrs O' Leary finally woke up from her nap and he rode her back to Sally Jackson's apartment. Sally was there, and she revealed that Remus had Flooed to Sirius's family house. Harry grabbed some Floo powder and invited the woman, but she declined.

Grimmauld Place hadn't changed much since his last visit, except for a gaping space where the portrait of Walburga Black used to be. Harry ended up straight in the living room, Sirius and Remus were there along with Dumbledore, Hermione and the Weasleys. Sirius had a sheepish grin, "Sorry… This was the best we could muster for now. Also, Albus felt that gathering everyone would only lead to more questions than answers."

There was a knock on the door, and a few minutes later, Thalia and the other Hunters walked in. Then the fireplace lit up again, with Professor Snape and Flitwick stepping out, with Hecate bringing up the rear. Harry dipped his head in respect, "Lady Hecate… Thank you for making it today."

He got everyone's attention, "Okay everyone! Listen, we don't have much time. Kronos and his forces are on their way to New York. Jackson and the other demigods are going to help defend Olympus. We need to help them as well."

Ron nodded firmly, "I'm with you, Harry."

However, Molly Weasley loudly interrupted, "Absolutely not! Ronald Bilius Weasley! You are still too young to be involved in this."

Her voice became softer and calmer, "I know I cannot stop Harry because this is his fight. Bill, Charlie and Percy, I can allow, because they are of age. I can also make an argument for the Twins. But you and Ginny are my children, and I love you. I trust Harry, but he can't be everywhere to protect all of you."

There was some arguing, before Ron, Hermione and Ginny were eventually dissuaded. By the time they were done, Sirius, Remus, Snape, Flitwick, Dumbledore and the older Weasleys were handed a few swords, spears and bows and arrows. Then Harry turned to Hecate, "Lady Hecate… I need to ask you a favour. Will you help us defend Olympus?"

The goddess of magic frowned, "Honestly, I have little love for the Olympians. But even I am aware that Kronos will be worse. Though I am sure you are aware, I cannot interfere directly. It is as the Fates have decreed. What I can do, is help you erect defences around Olympus. Potter, come here a second?"

He stepped forward and she placed a finger to his temple. In an instant, knowledge of a couple of powerful spells came flooding into his brain. When she was done, he staggered back and Fred steadied him. Hecate explained, "I'm sure that you want to protect the innocent mortals from the crossfire. Here's what you must do. The first spell is the equivalent to a Repelling ward, and it is powerful enough to envelope the whole of Manhattan. This will ensure that civilians do not enter the battle zone. I would suggest that you stand at the top of Olympus before casting the spell. The second spell is a ward that will strengthen the defences around Olympus itself."

Harry asked, "And the third?"

She replied, "I sensed the work of Morpheus, and he is putting all the inhabitants to sleep. Once the battle is over, you must be the one to awaken them. These spells are all one-time use and the knowledge will fade away once used."

Harry nodded and the combatants were off. One by one, they all Flooed back to Sally's apartment and exited.

The apartment was a few blocks away from Olympus, so Harry had to really book it. The Hunters headed straight for a safe house, with the wizards sticking with them. Harry entered the building and successfully negotiated with the desk clerk.

Before long, he was up on Olympus, and bumped into his fellow campers. Silena, Mackenzie and Fleur hugged him before going about their business. He noticed Hermes speaking to Annabeth and Percy, but neither of them had spotted him. Judging by the serious looks on their faces, he elected not to disturb them.

Finally, he stood on the edge of the throne room, overlooking the city. He unsheathed his sword and chanted the defensive spell. Almost immediately, he felt something tugging at his magic and the entire building was covered by an translucent shield that emanated from his sword, before fading. Then Harry dug deeper into his magical core and cast the second spell that Hecate implanted in his memory. This time, another translucent shield emanated from his sword and extended outwards. This shield was even bigger and raced well into the horizon before finally fading. Now exhausted, he collapsed on his butt and panted hard. Moments later, he felt a familiar pair of arms pick him up and haul him to his feet.

The smiling blonde visage of Fleur Delacour greeted him and he leaned heavily on her. She asked, "Are you okay, mon petit frere?"

He panted, "I'm fine, flower. That just took a lot out of me."

With surprising strength, she lugged him until he was riding piggyback on her. Just then, there was a shout from Connor Stoll. All the demigods had clustered around him as he pointed. At first glance, everything looked normal, but then Annabeth murmured, "I don't hear anything."

It all hit them, there was dead silence in the who of New York City. Percy glared at Harry, "Dude! What did you do to my city."

Harry weakly snapped, "This isn't me, you wanker! I'm not your bloody spy! I just strengthened some wards around Olympus itself. Then I cast a giant arse Repelling ward around the whole of Manhattan. This is the work of someone else!"

Silena came over and fed him some nectar and he was able to stand on wobbly knees. The girl exclaimed in astonishment, "Are they dead?"

The answer came from Percy, who mumbled aloud, "And see the world in endless sleep. Di immortales! So that's what he meant by main event!"

Except for Harry, everyone looked at him in confusion and he explained, "Not dead. Morpheus has put the entire island of Manhattan to sleep. The invasion has started."