RWBY: Dragon's Heart

The ground trembled and the surrounding castle ruins quaked. In a colorful blur of motion, Yin and King Tepes exchanged over a dozen moves in only a second. Yin's punches and kicks met the cold flesh of the Vampire King's fist and his bloody rapier.

[Mana Hike active]

Yin leapt back from a kick that further shattered the stone debris around them, leaping in the air and hopping across mana platforms. The King stayed his ground, though had his eyes trained on her even as she rapidly bounced around in the air.

*CRACK!*

Yin made her move, building up enough momentum to topple a skyscraper before striking out with her fist. Dust flew everywhere from the impact but Yin could see it clearly. The King had took her punch, blocking it right on time with a very quick kick that stopped her right in her tracks.

*VRRRR-*

Then there was a bright flash of red and Yin was forced back several feet, leaving deep grooves along the ground. Her aura flashed from the sudden strike but her eyes remained focused on the King. His magic radiated off him in a calm, focused manner. After he had blocked Yin's strike, he struck out with his mana, making it eject out of his foot, where he had met Yin's fist.

The two blurred once more, reaching an even more incredible speed. Yin threw herself completely into the fight, punching, kicking and clawing at the Vampire, becoming streaks of blue and red as their magical aura clashed against each other.

[Blazing Mana Claws active!]

Yin kicked off the King's blood rapier and swung both of her hands to the side, unleashing another massive burning slash. The King, seeing the attack coming bent backward and watched the flaming line of destruction pass by before reaching down, touching the ground and spinning his body around to dodge the flaming axe kick Yin had aimed at him after her last attack.

*WHAM!*

He then kicked Yin in the face after a quick spinning handstand.

Yin recovered mid air and once more planted her feet onto the shaky ground, glaring daggers at the unscathed King Tepes.

His moves lacked all of the unnecessary flare of the other Vampires. He was precise, not a single movement was wasted. When he struck, he hit. When he moved, he evaded. And most of all, his eyes never lost track of her.

'He's as fast as I am.. maybe even faster. And I'm using my semblance and acceleration. No clean hits on him and I haven't seen anything from him magically yet. Aside from his precise control of his mana.' Yin observed, continuing her attack and engaging him once more, this time utilizing her blue flames and the darkness magic to try and score a hit from behind him.

But it was as if he had eyes on the back of his head. The darkness spears she had utilized against the Vampires before had been avoided via the King's quick and precise footwork. He dodged her flaming claws, avoided the flaming wisps and outmaneuvered her Darkness magic. Yin was beginning to get frustrated. But along with that, was a rising impulse to destroy him. Like an unbearable itch she couldn't yet scratch. Gradually, her eyes began to take on a deeper purple hue.

Flames, Darkness and an Umbral violet energy began to emerge as Yin once again went on the offence.

-♤-☆-♤-☆-♤-☆-♤-

Yang had reached the remains of the Castle grounds, seeing her sister engage in an incredibly intense fight with the Vampire King. While she had full confidence in her sister, she realized something was wrong. Yin seemed almost psychotic the longer the fight went on. While she appreciated the raw, unrestrained aura her sister had when she saw her fight, this was different. It almost looked like she was in a haze.

*BOOOOOM!*

Yang watched as Yin created a gravity core, surrounding it in a massive amount of flames before directly throwing it at the Vampire King. But with a flash of bright crimson light, he created two massive sharp tendrils of blood that closed in on and pierced through the flames, all the way to the core of the gravity orb that held the spell together. As a result, the explosion engulphed the both of them and left Yin on the ground, panting with several burn marks marring her skin.

Her aura shattered from the detonation. Yang was about to run down when she realized she had yet to see King Tepes after the detonation.

"You really are a Destroyer, aren't you?" They both heard him speak, though from where, they couldn't tell.

"I suppose now, I can understand your arrogance." Yin's eyes widened as the King reformed from mist in front of her, rapier stabbing clean through her stomach.

"Kh..!" Yin grunted in shock and pain, feeling her blood being pulled out from within her.

Her blood from her wound traveled up the blade until it settled on the King's hand, creating a small red orb above his palm.

"A young Dragon. Not even over twenty either. Prideful creatures. It's a shame. Only fifteen and you've managed to get into Ultimate Class. Now you'll die like all arrogant young genuises." The King pulled his blade out and thrusted again, this time at her heart.

Yin tried to move, but her body felt rooted in place. Her eyes narrowed, focused on the impending death.

*CLANG!*

Yang leapt in front of Yin, bashing away the deadly rapier before throwing an explosive punch at the Vampire, her fist glowing white with her Light mana.

*HISSSS*

King Tepes held his arm up and blocked the hit. Though the hit made his skin bubble and blister before blackening, as if severely burnt. Yang then quickly grabbed her sister and leapt back, kicking off the ground with her light mana exploding out from her feet and briefly blinding the Vampire King.

"Sis! Are you okay!? He stabbed you.. Shit.. Shit.. I should have backed you up. Just hold on. I'll take care of this.."

Yin held onto her sister's arm until she pulled away and charged the King. Though he looked annoyed from the light magic that had wounded him previously, he once more began to evade, just as he had against her.

"Get up.." Yin muttered as she started to pick herself up off the ground while Yang took a powerful backhand across the face, her body smashing into the ground.

Yang stood back up, activating her semblance. Her hair became a light burning gold color and her eyes glowed red. Though to Yin, it seemed more like a small flame in front of a storm.

"And you're the Heroic one. What a pair you two made. The source of your power intrigues me but I have a promise to keep." King Tepes raised his hand and swallowed the little bead of blood he had taken from Yin, his body glowing with a violent crimson aura.

*CRAAAAASH!*

Yang raised her fists as the King briefly became a flash of crimson light. Like a comet, he brutally smashed into the Sunny Dragon with a guillotine kick. And though her arms were raised to block, the power of it sunk the entirety of the Castle grounds, along with the surrounding area of about two kilometers into a cave system underneath what used to be the Tepes Castle.

Yin blacked out.

-♤-☆-♤-☆-♤-☆-♤-

A myriad of thoughts, sensations and feelings overcame her.

'I was arrogant.. I have been arrogant. We didn't stand a chance against Sirzechs. We only managed to get out of there thanks to that combination of ourselves. Not that it would have been so bad to comply with him.. I let emotions dictate my actions lately. When it comes to Yang, I...'

She was cold. Dirt, stone and water pressed against her. Every part of her body was sore and wounded. Most of all was her stomach, where she was sure some of her organs had been pierced through. Most would go into shock but her Dragon physiology seemed to be doing its best to keep her active.

She regretted letting it come to this. She had underestimated the enemy and overestimated herself. She was uneasy, because Yang was fighting against that monster by herself. She was enraged, her pride had taken a heavy blow and she was worried. But letting her emotions dictate her choices led to this.

*Crumble*

Yin opened her eyes and began to dig herself out of the debris burying her.

Her pride and ego didn't matter. Her wounds didn't matter. Her fatigue didn't matter. Revenge didn't matter. The only thing that mattered was helping her sister.

Images of the past flashed through her mind. Of Yang being hurt by those Beowolves. If she had failed to buy her and Ruby time to escape.

Failure wasn't an option.

*Crack!*

Her hand clawed through the stone debris and she managed to pull herself up.

*CLANG!*

Yang and the King had clashed in the cavern. Yang had a long, sleek black blade on her hips and an improved Ember Celica on her fists. The Vampire King had been outspeeding her, forcing her to rely on the shotgun blasts of Ember Celica to enhance her speed just to dodge. It was frustrating, especially knowing her Light magic could seriously wound him if she got a clean hit in. On top of that was her worry of Yin. Her sister had fallen in too, which very likely only increased her injuries.

*BANG! BANG!*

Yang shot Ember Celica at the King's incoming rapier, propelling herself back just in time to get out of range. Though he didn't let up, continuing to pressure Yang with his sheer speed.

"Kh..!"

Yang grit her teeth. Being on the defensive wasn't working. Her aura was dipping into dangerous levels and very soon, she'd take a bad hit.

*CLANG!*

Yang once more shot the rapier and jumped over the next swing that came at her legs. She realized she was playing right into King Tepes' hands when he smirked and raised his other hand, radiating a blood red magical light from his palm, aimed straight at her chest.

*VRRR-*

A blue flash interrupted him before he could properly cast, having smashed into the back of his head. The King staggered forward, reaching to the back of his head with shock written all over his face.

"Sis..!" Yang called out, seeing Yin's disheveled and wounded state. Her piercing injury had been seared shut but aside from that, she was covered in little scratches and bruises.

"Yang. No time for debates or arguments. We have to take him together." Yin replied quietly, standing next to Yang. She then took out the Lightbreak blade from her inventory and held it out toward her sister.

"Take it. I can keep him on his toes. You'll need to dish out the damage." Yin muttered, her eyes watching the befuddled expression of the Vampire King.

"You seem different. Where did that psychotic smile go?" He mocked, though inwardly felt a sense of caution as the two prepared to take him on together.

Yin hyperfocused on the Vampire as she dashed at him once more, "Let's go."

Yang nodded and unsheathed the Lightbreak blade, following Yin's lead.

Yin stopped in her tracks, two centimeters from the King's rapier range and held out her hands, shooting a beachball sized azure fireball at his feet. The King was forced to leap up and avoid the explosion, seeing Yang had leapt up, Lightbreak blade held up, ready to cleave down into his body.

"Dangerous." The King muttered before turning into mist and letting Yang pass straight through him. He then turned around, returning to physical form while reaching his hand out to Yang's neck.

*THWACK!*

Only to recieve a flaming kick to the face. Yin's heel smashed his nose in and sent him sprawling back into the rocky ground.

"Peh..!" The Vampire King took a knee and spat out a glob of blood. He watched as both Yin and Yang prepared to engage him again. Their approach had suddenly become methodical instead of aggressively going on the offence as they had been until that point.

An unsettling feeling began to settle in his bones. Having lived for over two hundred years, he had fought many. Even Dragons. But nobody had done a complete 180 on him like this. His instincts told him to cut his losses and leave.

But to lose against children like this? After coming so far?

No. His pride would not allow for that. He was the successor of Vlad Tepes. The future King of all Vampires. The thought of fleeing from two children, Dragons or no, was unbearable.

"No more child gloves. I'm just going to kill you now."

[AN: I realized Yin was growing arrogant. And it's fine, mostly. Dragons are prideful beings. But I expect more from her.

Also, lotta fights now cuz in Vale she won't really go HAM. It's more a Criminal Empire building, acting, gang subjugation and some politics kind of arc. You'll also find more about the Mythic Grimm and the hidden powerhouses of this Remnant too.

It should only be one or two chapters until they return to Remnant. This DxD arc was more a means for me to have the sisters bond and fight together anyway. Thanks for reading!]