The ground of the cathedral was shattering as he avoided a powerful spell. Rhea´s body was releasing a powerful light from within; he could clearly see her green veins as she released her rage upon him.

"You can´t compare to my power, thief!" she shouted as her sword impacted against his own, blue and green sparks coming from their weapons with each blow. Edelgard was already on her, but she parried her attack with the shield of Seiros, a green aura coming from within the deepest part of the shield.

"You still dare to defy me!" An explosion happened, sending both of them flying. He could see how she was using her shield to push Edelgard against one of the walls. Even if she was using both of her crests, the fury in Rhea´s attack was truly unstoppable. The impact made crumble one of the walls of the cathedral as Rhea prepared herself to give the killing blow.

"Your bloodline ends here and now!"

"Not so fast!" he shouted as he used the whip form of his sword to trap Rhea´s arm, launching her against one of the columns of the building. The impact made the ceiling fell upon her, the cathedral menacing to crumble upon all of them. He was about to breath of relieve when he felt a strong power coming from within the ruins.

"I´m not done yet!" Rhea roared as she used the whip of the sword to launch him against one of the columns. He could feel how his bones shattered due to the impact, but the regenerative powers of the Crest of Flames were keeping him alive. Rhea was already on him, barely able to stop her thrust with the handle of his sword. He could feel the menacing cold coming from Rhea´s sword, while his sword was pulsating as if it was starting to beat like a living being.

"A usurper has no right to rule upon this world. Your fate is to die under my sword!"

"Our paths aren´t written, I will proof you that" he said as he charged his energy into the sword. With a strong attack he was able to break Rhea´s guard, his sword biting the flesh of her belly. From behind Edelgard released a charged attack that pierced through plate and flesh like hot butter.

Rhea crumbled on her legs, heavily bleeding from her injuries.

And then she laughed.

"You really think that you can defeat me like this? Another astounding failure from you, humans!" she said as ivory wings started to appear on her back, her hands claws sharper than most swords. "You must know your place in this world, you petty traitors"

"Careful, Edelgard!" he shouted when they were engulfed in a magic explosion. He was trying to find her, when a pair of claws grabbed him from behind and took him into the skies. The world beneath him was disappearing, only the clouds of the raging storm around them. He was trying to break free from her grab, but his efforts proved to be useless.

"You are too weak to compare to my power, your war was doomed to failure the moment you decided to fight against us" Rhea said as she flew even higher. White scales were starting to appear around her face, but the most unnatural feature were her eyes, looking at them was like looking to the sun, a powerful emerald light come from the depths of her body.

"I can´t allow myself to die by your hand, there is much I have to do before I die" he replied back as he accumulated power in both of his hands.

"Your life is mine to decide!"

"There you are wrong!" he shouted as he released his inner strength. The power of his magic weakened Rhea´s grab and in the split of a second, he was on top of her, his sword cutting the wings of Rhea off.

They were falling, the world beneath them dangerously approaching as they continued to fight against each other. He was bleeding heavily from Rhea´s attack, but she was as well. He was about to pierce through her heart, when both of her hands grabbed his head.

"Submit!" The power of Rhea was piercing through his body like lightning, his head feeling like it was about to explode as he felt how every bone withing him was breaking apart.

"I´ll rather die!" he said as the Sword of the Creator pierced through her body one more time, before it was too late. Released from her grip he could see how Rhea´s body was falling beneath him, but he didn´t have any energy to avoid the fall to his death. He was about to close his eyes, when he heard a familiar flapping of winds. His loyal mount was coming to his aid, its wings a new hope.

"Hello again, my dear friend" he smiled as he touched the Pegasus´s mane, when an arrow coming from below pierced through the poor beast´s eye. With a cry his old companion died, his body accompanying him in the fall.

"You bastard! You´ll pay for everything you have done!" It was Cyril. He had never seen him like that, pure hate pouring from his eyes. He was quickly approaching him using his mount, a black scaled wyvern. His axe was about to hit him, when it was stopped by another axe.

"You are another traitor! Rhea accepted both of you and yet you decided to side against her. You deserve to suffer a painful death!"

"One day death will come to us, but not today, of all lives you should be worried about your own" Edelgard said as she parried one of his attacks before slaying Cyril´s wyvern´s neck, the young boy falling to the depths of the abyss next to the monastery.

Reaching for her hand he was able to climb behind her, as they approached the ground.

"Thank you for saving my life" he was able to say. Despite being exhausted he knew that the battle was far from over.

"You would have done the same. But this battle is far from over" Edelgard said as they prepared to land. The land had shattered where Rhea had fallen, yet he could feel a strong energy coming from the destroyed boulders.

The battleground around them was scattered by the corpses of the fallen combatants, but the battle was still raging around them. Among the troops of the Church he could see that Catherine was quickly approaching their position, her Thunderbrand glowing like pure fire.

"I´ve been searching for you, traitor. Your time to pay for your crimes has come at last"

"Wait Catherine. He is mine" said a voice from the depths of the ground. Rhea was standing once again, green blood still pouring from her head. "Did you really think that a little fall would destroy me? The punishment for you has just begun!" Rhea said as her body started to change, her neck growing longer as a new pair of wings appeared on her back. In a few seconds the Rhea he knew was no more, a giant ivory dragon in front of him. "Catherine, get rid of the child, I don´t want her to pester us any longer"

"Rhea…Understood" Catherine said with a quick nod as a reaction to the sudden transformation of the archbishop.

"Don´t worry about me, I can take care of her" Edelgard said as she prepared to face Catherine, the duel between both worlds about to start.

…

"You are a weakling, you are just blocking my attacks, you are too slow to hit me, old man" he said as he tried to cut the neck off of the old man in front of him with his scythe.

"You were an instructor at this place as well, Jeritza, yet you have come to this place to bring more unnecessary destruction. I´ll protect the king with my life!"

"I´m not interested in that little boy, I told you. The monastery is about to end in our control, you would be wise to surrender"

"Not with scum like you, a bastard that kills innocent without blinking an eye. You are a monster!"

"And you are correct, I´m a monster and I don´t pretend to be otherwise"

"Have you ever felt guilty about the crimes you commit? Do you have any soul under the helmet you use to cover your face?"

"I used to have one, not anymore"

"Only a coward hides behind a mask!"

"And only an idiot would not be being using a helmet at the battlefield, now die, you are boring me" he said as he charged his scythe with a thunder spell. The shield of the old man finally was destroyed. Gilbert tried to hit him with the battle axe, but was exhausted and failed the hit. With a jump he ended up behind him as he used his scythe to cut the tendons of his feet off. Unable to move or stand up, Gilbert tried to fight back, but he knocked him down to the ground with a hit to the face, which broke his nose.

"Are you ready to die?"

"If with my dead I can save his majesty then I will honorably take it"

"There is no honor in death, you only speak nonsense" he prepared to finish him off when a magic spell impacted into him sending him to the ground. He could sense he was bleeding, an ice javelin piercing through the plate of his armor. The author of such spell was a red-haired girl, that hurried up to Gilbert´s place.

"Father! Are you ok?"

"Annette, you must leave this place…his Highness must be protected, this battle is lost, the monastery is gone"

"That was an impressive spell, young girl, but it isn´t quite enough" he said as he stood up again, but his advanced was stopped as three more students appeared.

"The Death Knight, uh, a worthy opponent at least"

"Take it easy, Felix, this is not the time to get cocky"

"If it weren´t by me all of you would be in a mess already"

The three of them were holding relics. Things were about to get interesting.

"If you are so confident about your skills, then come at me with all you have"

The young boys were strong, but they were reckless in their attacks and left too many openings. With a thunder discharge he got rid of the red haired one while he parried one attack from the swordsman, before quickly exchanging a blow against the blonde woman. The styles of both combatants were completely different. While the young girl was measuring every attack, before trying to aim at the junctures of his heavy armor, the young man was trying to overcome him with sheer strength.

"I feel rage in you, you don´t fight like your friends"

"I don´t fight like a knight, if that´s what you are saying. You are a tough opponent. Enemies like you is what I need if I want to get stronger"

"Then allow me to show my force" he said as he used a wide dash to parry both of the attacks aimed at him. The blow was so strong that sent both of his adversaries to the ground. He was approaching them when an arrow hit him from behind. When he looked behind him, he could see a grey-haired young boy with green eyes at one of the roofs.

The next thing he felt was a piercing pain. When he looked at his stomach, he could see a couple of ice spears biting his flesh. He was preparing to attack the red-haired girl, when he received the attack from one of the relics, the red-haired man was standing up again, although he was breathing with difficulty.

"This pain…is nothing. Are you going to claim the price?" he said as he looked at them.

"I´ll do it" Gilbert said as he slowed approached him, accompanied by his daughter. "You are a monster and I can´t let them to have your filthy blood in their hands"

"You really think that you have the moral high ground, but you are a murderer just like me" he chuckled. "The only difference is that I´m not willing to continue the farce of knighthood. I´ve killed people like you all my life; you feel highly of yourselves, but in the end, you are nothing but scum"

"Enough of your insolence. Jeritza, I don´t know how you ended up like this, but I will put an end to your existence now" Gilbert said as he raised his axe.

"Too slow" he thought as he avoided the hit. A quick counterattack disarmed him as he cut through his leg, making him fall to the ground. The young boy tried to react, but he was faster and he left him unconscious with a spell to the chest. He was avoiding one of the arrows of the other when he saw a silver lightning from behind. He was barely able to avoid the attack. Looking at his attacker, he realized it was Gilbert´s daughter.

"I won´t let you kill them!"

"Killing or being killed that´s the only reason to exist in this world. Everything else is a lie, a lie that only serves to make us feel safer"

"Your mind is twisted if you really think like that"

"I´m the monster that everyone needs. Everyone needs something to hate if they want to fight together. I see hate in your eyes, try and kill me if you are willing to act according to your words"

Scythe and axe impacted against each other, sparks coming from his weapon. Charging his scythe once again he attacked her, but the moment that the scythe met the axe an explosion sent him to the ground.

"You charged your weapon with protective magic, smart"

"I´ll put an end to this!" the young girl said as she charged at him.

"Stop! Don´t do it" a young woman he knew too well said as she stood between her and the rest of the students.

"Mercie, what are you doing? He is a monster, he is a murderer, he is…"

"He is my brother, Annie and even if he has turned into a monster, I still love him" Mercedes said as tears started to leave her eyes.

"Mercie…"

"We have to leave this place immediately" Gilbert said as he looked at the distance. Alois was leading what remained of the Church troops as they were evacuating the monastery. "We have no more time" he said as he took care of a still unconscious Dimitri.

He was feeling weak after the battle, but he was feeling even weaker with her presence in front of her.

"Leave me"

"Now that I have found you, no Emile, I´ll stay with you and I will find the truth about what happened that day" Mercedes said before looking at Annette. "Annie, I´ll stay here, take care of the others for me"

"But, Mercie…if you stay here you will be imprisoned by the imperial troops"

"Don´t worry about me, I hope I can see you once again…at a more peaceful time"

"Mercie…" Tears were starting to leave Annette´s eyes, but the sound of battle was coming closer. "it´s a promise then. Be safe, we´ll meet again!" Annette said as she casted a spell to bring her unconscious friends into safety.

"I will pray for you as well" Mercedes said as she observed how her friends left before taking his helm off.

"What happened to you, Emile? Why have you been hiding your identity all this time"

"You should have run away with your friends, run away to a safer place"

"I did it once and I regretted it all my life I won´t do it again. I´m your sister after all" Mercedes said with a sad smile as he looked at him, and for an instant he felt like he was a child again, when the world was simpler yet more beautiful.

But those times were far gone, only death and suffering remained within him.

"Leave this place, it´s not safe anymore" he said as he saw the explosions happening on the battlefield miles away from them.

"I told you…"

"I know, but this is not the place to talk. I need to make sure to talk to you later, until then leave me alone" He said as he put his helmet on again, leaving his sister behind.

….

"The immaculate one has appeared, my lord"

"Finally, the final battle has come at last, we´ll crush both the fell star and the beast to assure our victory upon our enemies. Prepare our remaining troops to finish the assault"

"Understood"

…..

"In ancient times I used my true form to battle against our enemies. With this power I have never met defeat" The immaculate one said as she released a potent beam against him.

"Even the strongest warriors can have a defeat, and this will be the day of yours, Rhea"

"Don´t you understand? Sothis trusted me with the future and security of this world. Opposing my will is opposing the will of our creator"

"Sothis would have refused to perpetuate a world of inequalities"

"You know nothing about true suffering. If this world suffers is because of your wicked brethren, you should have been exterminated yet we were merciful enough to let you escape from your fate of extinction yet you are using what remains of my mother against me!"

"The crime committed on Sothis´s body is something I will avenge, but you can´t keep reigning over Fódlan. The fights of power, the death and suffering of many are consequences of your authority. I won´t use this sword to commit the atrocities you suffered ages ago"

"Your words are nothing but lies!" Rhea roared as she smashed the ground with her tail. Rhea was freezing the land around them with her potent beans, as he continued to repel her attacks with his sword. Ice and fire were impacting against each other while he danced around the Immaculate one. With each opening of her attacks he was able to attack the ivory scales, but she didn´t appear to be suffering great pain from them.

With each attack he could feel a stronger energy coming from the Sword of the Creator. A few meters from him, Edelgard was fighting against Catherine with everything she had; Catherine was looking for openings but Edelgard´s reach allowed her to keep her distance from her.

Rhea´s beam destroyed the land a few meters of him, but taking advantage of the opening he jumped on her head. He could feel and increasing strength coming from within his body as his Sword started to pierce through the scales of her skull. Rhea was roaring as she was trying to shake him off, her claws and tail trying to hit him in the process, but he continued nevertheless. He was about to succeed when an explosion made me him lose his balance.

They were shooting at them; monsters and giants of steel were attacking them as the giant creation of the Argarthans was approaching as well. Rhea tried to fly away, but giant chains trapped her as a giant hand took her.

"The cycle ends here" A metallic voice from within the giant said as Rhea was imprisoned between the creature´s hands. It then opened its mouth releasing a power beam against her, before brutally smashing her body to the ground, the land trembling as if an earthquake had just happened. And then the land around the crater was engulfed in potent explosions all kind of spells and weaponry used to annihilate whatever that remained alive after the brutal impact.

"I´ve waited a long time for this" Thales laughed as the dust started to fade away. After such attack it was impossible that she could have survived, yet he felt the battle wasn´t over yet.

"You mortals can´t understand the nature of divinity!" roared a voice from within the deeps of the earth as torrents of water started to fill the huge crater. "Mother, give me your strength, the power of the ancestors and help me to defeat my enemies. Give me the strength to achieve our revenge!"

A giant claw emerged from the crater, its ivory scales shining with new light as the Immaculate one raised once again from abyss, but it had changed. Its horns had acquired a heavenly blue color, while its eyes were filled with red rage.

"Filthy Argarthan, enemy of everything that is sacred. Today I will achieve my revenge, there will be no redemption for your souls, all of you shall perish upon my fury!" Rhea roared as her horns started to get even more brilliant. She then flew into the sky.

"Shoot her down!" Thales roared as all kind of projectiles flew over the sky, but all of them fell to the ground, frozen when they approached the celestial dragon in the sky.

"Edelgard, with me!" he shouted as he erected a magic barrier around them, the Sword of the Creator acting as a catalyst.

Rhea´s body was pulsating with its own light, a silver moon in the middle of a raging storm, even the everlasting rain had stopped as Rhea´s body grew brighter. Around them, the troops of the Argarthans were desperately trying to erect barriers while some of their units were trying to shoot Rhea down.

And then death descended upon the land.

A monstrous beam impacted into the ground sending a shockwave of true cold. He was feeling like his head was about to explode as the first cracks started to appear on their magic barrier.

"Stay with me!" said a softer voice next to him. It was Edelgard, who was placing her hands on the handle of the sword in the same way he was doing to keep the barrier working. Around them he could hear all kind of cries and explosions…

And then nothing, but silence. The barrier finally broke apart, but they were safe.

"What has happened to the world?" Edelgard muttered as she gave a look to the battlefield. There was nothing, but ice, broken weapons, beasts and humans scattered among the ice. Not even the giant colossus was left intact one of its legs, an arm and half its face destroyed by the strength of the attack.

"This is the power of the descendants of the Goddess. The water of desperation turned into ice by me fury" The Immaculate´s voice said from the heights, its voice a thunder. "Your armies had been destroyed and I´ve annihilated my ancient enemies, but it isn´t enough. Only death will purify your souls and those who are opposing to our divine rule" the majestic beast said as she started to grow brighter.

Another blast would certainly mean the end of them all, but there weren´t any options left. Were they doomed to die before a beast from ancient times?

He was still thinking when he felt a warm hand on his cheek.

"We can´t give up on hope, there is still much that needs to be done, falling now would achieve nothing but more pain and suffering"

It was true and her words gave him what he needed the most; hope.

As the Immaculate one grew even brighter, he closed his eyes, searching in the inner deeps of his soul, a giant crest appearing in front of him. When he opened his eyes, the Sword of the Creator was covered in flames, its length and size increased.

Light came from the Immaculate one once again, but this time he was prepared. Releasing all his powers through the sword, the flames met the ice of death. He could feel the strength behind Rhea´s attack, as the sword was demanding all of his energy, but he resisted. And then golden flames engulfed Rhea´s body as an explosion lightened the sky upon them.

The Immaculate one collapsed upon the ground with a roar. With its fall, the clouds of storms upon them started to disappear, the water that had been there since the beginning of the battle coming to an end.

"I can´t be defeated by someone like you, a traitor and a thief" Rhea roared, there were areas of her scales that there were partially melted, but her horns were still intact, monstrous amounts of energy still coming through them. "You might have been able to stop me once, but I won´t be stopped by you!" she roared as she ran upon them on her four limbs, her jaws wide opened as a blue light was accumulating within her.

"It´s going to shoot again!" Edelgard shouted but he was already charging at the Immaculate One.

"Take care of the rest on my behalf"

"No…wait!"

But the ancient beast was already on him. It released a beam of death as he released a thunder of fire through his swords as he jumped on the dragon´s chest.

"There is only one try" he thought as he unleashed what remained of his energy upon the beast´s chest. The explosion that followed, made the beast lose its balance, as the sword beneath it crumbled. He was about to jump away when a giant claw grabbed him.

"If I fall you will fall as well!"

They were falling, he tried to use his sword to stop his fall, but it failed. The world around him were just rocks and the roars of the immaculate one as the underground river beneath them grew bigger by the second. His body was exhausted, no energy left after all that had happened.

He then felt a freezing cold as darkness engulfed him.

Since 天帝 means celestial emperor I think that you could name the children of the Goddess as 天竜, celestial dragons. Talking about dragon biology, Rhea is capable of storing great amounts of water within its body, which they turn into ice the moment they leave her body.

I won´t be jumping directly into the timeskip in case you are wondering.