Author's Note: This was actually going to be two different oneshots, but it just felt right to merge them. I know I should be writing more of Fort Olympus, but my muse was bothering me for this for a long time. I had to write this.

Also, I couldn't return to studying for final exams until I wrote this, so I couldn't ignore my pestering muse. I blame Lord Apollo... He's the leader of the Muses, so he deserves my blame for distracting me from my work, right? XP

Anyway, enjoy this piece! I always thought it would be kind of cool if the Prophecy and the Seven ended up differently than how Riordan is portraying it right now. And this is my interpretation of "An oath to keep with a final breath".

As always, please read and review! :D Thanks!

Disclaimer: Percy Jackson and the Olympians and The Heroes of Olympus and all things related are property of Rick Riordan and Disney Hyperion. I am not making any profit off of this work in any way, shape, or form.

No. This can't be happening! Nico rushed to where Reyna had fallen.

After returning the Athena Parthenos to Camp Half-Blood, the two armies of demigods had set off to the original Mount Olympus to help the gods and the Seven win the war.

Reyna and he had gotten quite close on their trip back across Europe and North America. They'd found many things to bond over, including their mutual ostracization, and… their lost love(s). She had apologized for treating him like a freak in the past, and he had shared some of his more cherished memories, finally feeling like he had come across someone who truly understood him.

She'd told him that she had truly loved Jason, and that one of the main reasons she'd agreed to travel to the ancient lands was so that he might notice her.

All these memories passed through Nico's mind as he rushed towards the sound of Reyna's scream for help. With tears in his eyes, he saw the arrow in her abdomen. Somehow, it had pierced her armor. He knew it was too late. He was the Prince of the Underworld; he knew when someone was taking their last breaths.

Out of the corner of his eye, he saw Jason running towards her, too. He resisted the urge to kill the blond-haired jerk for hurting Reyna so much, even if it was inadvertently.

Nico caught Reyna by her waist just as she fell over. Tears streamed down his cheeks as he slowly brought her head into his lap.

"Reyna," he whispered anxiously. He knew he couldn't love her. He knew he didn't. But she was one of the few people he had learned to respect and care for… And he knew that she cared about him, too.

Reyna opened her eyes. She gave him a tired smirk. "What're you looking so sad about, Death Boy?"

Nico gave a half-hearted laugh. "Why?" He whispered.

She smiled at him in pain and content. "It's my fate."

Nico shook his head. "That spear was supposed to be for me. It was coming my way… Why did you intercept it?"

"You're not done yet," she said softly, staring deep into his eyes. "My role ends here, but yours is just beginning."

Nico noticed the Seven watching them, standing around him and Reyna in a protective circle, effectively cutting them off from the rest of the battle. He saw Jason standing right in front of them, slightly closer than the rest of them. Yet again, Nico resisted the urge to attack Jason then and there for both being witness to his weakest moments and for hurting Reyna so much in the past.

"You don't know that," Nico said softly, pushing a stray strand of hair out of her face. "You couldn't have known that."

She just gave him another tired smile. "Call it a hunch, then, Nico. But no matter what, I'm proud to have called you my friend in the end… You're a good warrior and a great listener. You have a great future ahead of you."

Nico felt tears falling from his eyes again as he watched the Warrior Queen say her last words.

She reached her hand up. He grabbed it and brought it up to cheek. She smiled and caressed his cheek as tears continued to fall from his eyes.

"Thank you," she said in the end.

She dropped her hand and turned to Jason.

"Jason, I'm sorry for the past. After talking to Venus in Charleston, I never treated you as well as I should have. You were a good man."

Jason flinched, and Nico rolled his eyes. It should be Jason apologizing for hurting her, not the other way around.

"I'm sorry, Reyna," Jason said finally. He at least had the decency to sound legitimately pained. His eyes were watery, and he looked like he was going to unleash a torrent of words to express his sorrow. "I'm sorry for leading you—"

Reyna shook her head. "Don't," she all but growled.

Jason took a step back at her contempt.

"I want neither your apology nor your pity, Jason," she spat out. "The past is the past. You've found happiness elsewhere. Enjoy it."

Jason's jaw dropped at Reyna's harsh words. Nico found a morbid sense of satisfaction at that. Jason deserved to feel at least some of the pain he'd inflicted on the Warrior Queen who had loved him with her whole being.

Piper took Jason's hand, and it looked like she was about to explode. But Jason shook his head at his girlfriend.

Reyna turned back to Nico. She chuckled.

"Thank you for being my friend, Nico," she said softly, "after everyone else abandoned me."

Nico nodded, not trusting his voice to speak.

She chuckled weakly. "Venus really does hate me."

"What're you talking about?" Nico asked in confusion.

She looked at him with a pained smile. "It doesn't matter. Can you fulfill my last wish, Nico?"

"Of course!"

She struggled to lean up and whispered something into his ear.

His eyes widened in shock, but he nodded.

"Scram!" He ordered the rest of them.

At his death glare, the Seven returned to the battle to assist their brethren and their parents.

She smiled up at him. "I really do have a weakness to Sons of the Big Three. First Jason, then Percy, and now you…"

Nico looked down at her in shock. "Me?"

She coughed but grinned up at him. "Yes, you," she whispered.

"But… I'm just me."

She laughed weakly. "You're brave, you're loyal, you're a natural leader, you're a strategist, and your independent. I've always admired those qualities. Either that, or Venus enjoys screwing with me a lot more than I'd initially thought."

"But you love Jason," he protested weakly.

She shook her head. "I used to like Jason."

"Reyna..." he began softly. "I can't like you."

She smiled. "Trust me, I know. It's okay. I'm used to the guys I like not liking me back at this point," she said bitterly.

"No, it's not that… You're amazing… It's just that I'm…"

"Nico, it's okay," she cut off, "I know."

He looked at her in shock.

She smiled at him. "I figured it out," she whispered.

He nodded with pain in his eyes.

Then he stared at her again, her black hair tumbled across his black and her eyes as black as obsidian. In the evening light, she looked to be glowing, and he could feel her soul slowly making its final journey down to Hades. He'd learned to appreciate her as a companion and definitely as both a warrior and a leader.

His eyes darkened with grim determination, and his jawline became more firm.

He leaned down and captured her lips with his own. He barely saw her eyes widen before they both closed their eyes and she kissed him back with all the passion and belief that he knew she had been hiding for all these years.

Dimly, he heard Jason gasp next to him, and he knew that the Sky Prince was staring at them. He didn't care.

Kissing Reyna didn't do anything to him, but he knew that this was her last wish. She'd always wanted her first, and in this case her last as well, kiss to be with someone she loved. She had admitted that when they were in Paris together on their way back. He was glad to be fulfilling her last wish.

Finally, they pulled apart, and Reyna grinned up at him weakly. "Thank you," she said softly.

Nico grinned back at her and stroked her hair.

She looked at him one last time and said what were sure to be her last words. "Nico di Angelo! I, Reyna Avila Ramirez-Arellano, praetor of the Twelfth Legion Fulminata, give you my final order. You are a true Roman at heart despite being born Greek, with all of the loyalties and individualities of a Roman. I resign my post and give you emergency field promotion to praetor, with full powers of that rank."

At that last word, she closed her eyes, and he knew that her soul was on its way across the River Styx.

He looked at her in shock but put her down gently on the ground. He stood up, still in a daze at what Reyna had just ordered him to do. But there was new feeling of power in him, as though he could throw a bull over a castle.

He saw Jason standing in front of him. He saw nothing but the red of fury and hatred. He drew his sword and charged into battle, ignoring Jason.

He used his fury at the idiotic Sky Prince to cut through legions upon legions of monsters. His Stygian Iron blade became an arc of terror, blazing through ranks of monsters as though they were paper. Dimly, he was aware of the black fire that surrounded his sword. Hellfire, he thought grimly. It was one of the weapons used to torture sinners in the Fields of Punishments.

With a gruesome grin, he charged. He didn't even recognize himself. All he knew was that he wanted the world to pay for taking away the warrior queen from him, one of his only true friends, and one of the only people who actually loved him. In the deepest recesses of his mind, he knew that he was looking the exact same way right now as Percy had when Hades' armies had attacked them on the banks of the River Styx last year. He was even more terrifying than Percy, though.

He took a breath to steady himself and saw that he was surrounded by monsters. In desperation, he drew the scepter of Diocletian from its sheath at his waist. He raised it and summoned a legion of ancient Roman legionnaires.

Only an officer of Rome can command them, his conscience told him. And you're Greek. You won't be able to control them. They will go crazy. Send them back while you still can, it urged.

Nico growled at himself. "Legion, form ranks," he barked.

Immediately, the undead warriors formed into lines of soldiers.

With a self-satisfied smirk, he gave his next order. "Lock shields. Break into five units. Attack in pincer formation. Take out those monsters."

The legion answered his commands.

Looks like I'm a Roman at heart after all.

"How did you do that?" Jason exclaimed from next to him.

The rest of the Seven were looking at him in shock, especially Frank and Percy.

He glared at each of them individually before punching Jason in the gut. Jason doubled over in pain. Nico grabbed him by the collar down to his level. He was satisfied to see pure, raw fear in Jason's eyes.

"That was for hurting Reyna, you bastard," he spat. "Do you have any idea how much she loved you?"

He threw Jason back, and the Sky Prince flew ten feet back before falling over in a daze. Piper immediately went over to help Jason.

Nico glared at each of the Seven individually. They all cowered before him, leaving him half satisfied.

He shot his left hand towards the sky. The sky darkened at his movement, and the shadows became longer and blacker.

"TWELFTH LEGION FULMINATA!" He screamed. Thunder boomed throughout the battlefield, and lightning struck at his pointed fist. In his outstretched left hand, the Twelfth Legion's eagle materialized. Lightning struck again, and he heard cheers around him.

"Legion!" He ordered across the entire battlefield. His voice carried as though it were amplified by a thousand Nicos talking together.

"Form ranks!" He barked. "Lock shields! Archers, target the Giants. Infantry, forward march! Take those battlements, and storm Mount Olympus! For Rome! For Jupiter! For Zeus! For Greece! FORWARD MARCH!"

Immediately, the legion of undead soldiers marched towards the mountains. The Twelfth Legion scrambled to order and marched with renewed vigour.

Nico watched in annoyance as the the Greeks merely looked at their Roman compatriots but made no move to attack.

"Greeks!" He yelled. "STRIKE FOR THE LEGACY OF THE WEST! RETAKE MOUNT OLYMPUS! ATTACK THE ENEMY! BATTLE FORMATION 84 DELTA, ACTIVATE!"

The Greek demigods immediately answered his orders and charged into battle.

Nico growled when he noticed that the Seven weren't moving. "Are you buffoons just going to stand there or fight?"

Annabeth was the first to find herself. "Take us to the front of the armies," she told Nico.

Nico nodded. "Hold hands!" He barked.

Once the Seven gathered in a circle with hands held, Nico shadow traveled them to the front of the advancing armies. He turned to face forward, the Legion's eagle in one hand and his Stygian Iron sword in the other.

He thrust his left hand forward, and lightning struck the nearest peak.

"GREECE! ROME!" He screamed to the armies behind him. "YOU ALL ARE THE GREATEST HEROES THE WORLD HAS EVER KNOWN. YOU HAVE SURVIVED THE BATTLE AGAINST THE TITANS AND NOW ARE FIGHTING AGAINST THE GIANTS. NO DEMIGOD HAS EVER DONE THIS BEFORE. STRIKE FOR THE SAKE OF OUR FUTURE! STRIKE TO SECURE OUR OWN PAST AND ESTABLISH A BRIGHT LEGACY!"

The Seven flanked him on either side, so that the eight of them were in a rough triangle formation.

They charged with Nico in the lead.

Nico attacked with a rage never seen before. He remembered everything he'd lost: his mother, his father, his sister, and finally his friend in Reyna. He remembered how Gaea had tried to kill him in Tartarus and out of Tartarus. He remembered how he was made a mere pawn in the overall chess game.

The earth seemed to chuckle around him. "Ah, yes, the great Nico di Angelo. I was wondering when you'd realize you were part of the Seven."

"Get away you witch," he growled as he skewered a dracanae with the eagle standard.

Gaea's voice laughed all around him, and he saw the goddess rising from the mountain. "You cannot defeat me, hero," she said, amused. "It is too late. I just await the sacrifice to awake from my slumber."

"I will never let you rise, you bitch," he snarled.

He thrust the eagle towards the goddess again. Lightning struck her, and she stumbled backwards before straightening.

"Ah, my grandson's blessing. Good luck." With that, the form of the goddess shrunk back into the earth.

Nico snarled. "ARMIES OF OLYMPUS!" He screamed across the battlefield while parrying the strikes of a empousa. "STRIKE NOW! RAIN DOWN DEATH UPON OUR ENEMIES!"

He raised the eagle and his sword once again.

"I stand before you as both Greek and Roman! I stand to show you that the future is still ours if we choose so. Attack now! Make the giants rue the day they chose to be reborn!"

The armies of demigods attacked with renewed force. Monster dust and human blood littered the battlefield, but nothing stopped the arc of sheer destruction that Nico had created out of his fellow demigods.

The gods struck the mountain, the focus of Gaea's power, with renewed force. The earth around them seemed to shiver, and Nico could see Gaea's scowl in his eyes.

"I will destroy you, hero," she promised him.

He remembered the taste of Reyna's lips on his, and he was drawn into rage all over again at the memory of losing her.

"Not on my watch, bitch."

He struck once again, and this time, he could feel the gods and the Seven join him in the attack.

Zeus struck with this master bolt. Thalia and Jason unleashed a barrage of lightning and storm fury. Athena and Annabeth called orders while launching spears towards the mountain. Percy and Poseidon were commanding the Aegean Sea to surround the mountain. The other gods were striking together. Hades and Hazel struck with surface-to-surface missiles from the Earth itself.

The giants had long since been defeated. All that was left was the Earth Mother herself.

Gaea growled once more before as Hypnos forced her back to sleep.

"Nico di Angelo, you promised that you would leave forever after returning the Athena Parthenos. You will do so now," the Earth goddess' voice echoed all across the battlefield.

With a roar, Nico charged to the mountain. He thrust the eagle one more time, blasting a peak off with lightning. He pushed his sword forward and shot the mountain with a blast of hellfire. An entire outcropping become lava.

Gaea chuckled. "I return to my slumber, now, young ones. But I take your commander with me."

Nico continued to run forward but suddenly stumbled.

He looked down to see a spire from the Earth piercing his abdomen.

"Good night, heroes," Gaea said. The smirk in her voice almost seemed audible.

Hypnos finished his enchantment, and the Earth Mother returned to her sleep.

Nico fell on his back, the eagle and sword still in his hands.

He dimly was aware of the Seven and the gods approaching.

"An oath to keep with a final breath," Hera said softly. She was looking at Nico with pain in her eyes. Tears were streaming down her face. "You promised that you would leave us after finishing your duties." Hera knelt down and placed her right hand over his wound, which was oozing blood. She muttered an Ancient Greek blessing. "Be at peace, my nephew." The Queen of the Heavens pressed a kiss to his forehead before closing his eyes.

The gods looked at each other in grief. The true leader of the Seven was dead. Despite his hardships, troubles, and tribulations, Nico di Angelo had fought for Olympus in the end. And he had paid the ultimate price.

"Nico di Angelo, Son to Hades and Pluto, Champion of Hestia, Prince of the Underworld, Heir to the Sacred Hearth, King of Ghosts, Master of Shadows," Zeus announced solemnly, "Commander of all Greek and Roman forces is dead."

Hades fell to his knees before his son, taking his head into his lap. Persephone laid a comforting hand on her husband's shoulder.

"He was one of the Seven," Leo whispered.

"Yes, Son of Hephaestus," Hera said softly, tears still pouring out of her eyes. "He was the most important player in this game. He was the most powerful of all demigods."

"So which of us wasn't?" Annabeth demanded the Queen.

Hera turned to Annabeth with a stony gaze, but her grief over Nico's death was still seen in her eyes.

"Perseus Jackson was never a member of the Seven," the Queen announced.

There was a collective gasp. Percy looked at Hera in shock.

"But you told me I was!" Percy protested.

The Queen looked at him with sadness. "I told you that you would unite the Seven and that you would serve as the glue to hold them together instead of destroying each other," she reminded Percy. "I never said you were one of the Seven. You have already saved the world once. This time, you were simply the keystone that kept the whole crew from falling apart. Nico di Angelo is the only demigod to ever be born to a Unified Greek and Roman god. When the Lord of the Underworld met his mother for the second time, he appeared to her in his near-true form: as both Hades and Pluto. Nico di Angelo was born from this union. And it is because Nico di Angelo was both Greek and Roman that the ratio of Greek to Roman was balanced in the Prophecy. If you were one of the Seven, Jackson, there would have been an imbalance with four Greeks and three Romans. But with Nico di Angelo, there were four Greeks and four Romans with only Seven total. He was the true leader of the Seven, because he embodied both Greek and Roman values. He was my Chosen One."

Hera returned to Nico's body. She put her hand over his heart. "Nico di Angelo was my chosen hero. His fate was to free the world from its terror. He was born to lead the Greek and Roman demigods into battle together. He was born to bring the two halves of our family together. He was created to unite us all. He took on a great responsibility with even greater pains. He won in the end. He is the greatest hero of all time. Let his name and story never be forgotten! My Nephew, bards will write legends about you and your greatness for all time. You will be even more famous the all of the great Greek and Roman heroes. Your name will be ranked above Perseus, Heracles, Jason, Odysseus, and even Achilles. Let your legacy guide us to a better future. Thank you."

Poseidon raised his trident to strike Hera at that remark.

"Brother," Zeus stopped him. "We are all proud of our children. Perseus Jackson is one of the greatest heroes of all time. But our sister is right: Nico di Angelo will be remembered as the greatest to ever grace this Earth. Peace."

Poseidon glared at his brother but nodded, looking unhappy about the news but accepting it no less.

Hera turned to the Seven and the demigods assembled. "Nico di Angelo was praetor of the Twelfth Legion Fulminata and a leader of the Greek demigods. We put him to rest now."

She turned to Hades. "Brother, take him for the past, the present, and the future. He was the greatest demigod of all time. He deserves to achieve peace."

Hera turned back to the demigods. "Return to your homes. Rebuild. Welcome your past, open your eyes to the future. Hold elections. Be the ones to accept yourselves. Be at peace."

With a wave of her hand, the demigods vanished to return to Camp Half-Blood. Only the Seven remained on the battlefield with the gods. They watched Nico's lifeless body.

"He was my pride and joy," Hades whispered.

Hazel ran to her brother's body, sobbing. "You were the best brother I could ever ask for. I love you, Nico."

Hades comforted his daughter.

The rest of the Seven approached to pay their respects to their fallen hero.

Nico di Angelo had honored both Reyna Avila Ramirez-Arellano's last wish, as well as his own.

Author's Note: My friend and I used to debate whether or not Nico would be one of the Seven after The Lost Hero came out. He said Nico would be, but I always claimed Nico wouldn't be. In the end, I was right; I was able to name all Seven heroes of the Second Great Prophecy as Riordan wrote in his books. However, I always had a morbid fascination with the idea of Nico being a child of the Great Prophecy, and this fascination only became deeper after we got to hear about his hardships in The House of Hades.

I decided to explore it a bit more. Also, it's no secret that I'm a huge fan of the potential bromance between Reyna and Nico as they travel back to New York. :P I've been exploring it in Fort Olympus, and I wanted to explore it even more. I want to reiterate that Nico did not like Reyna in here. I can't bring myself to write Nico as even bisexual, let alone straight. After what we learned in The House of Hades, I feel like it would be a disservice to his character if I write him like that. In this one shot, all Nico was doing was honoring a close friend's last wish.

Oh, and like I said before, this was actually going to be two different oneshots. I had separate plot bunnies in my head for both Nico dying in the final battle and Reyna dying in the final battle, but it seemed right to merge them into this one. I think it turned out well.

I hope you guys liked it! I really had fun writing this even though it didn't quite turn out how I wanted it to. Oh well!

I will hopefully have the next chapter of Fort Olympus out in another week and a half or so. If you get a chance, please do read that fic and leave a review telling me what you think!

And please leave a review telling me what you think about this little oneshot I whipped up!