"Huh, Shizuka really went all out in that battle. At least sleep is a thing for both of us." the twin sister of the sun prince said to herself. She had returned from a hard day of training with her blader. After having a nice drink at one of the taverns at The Heart, Selene walked back to the castle. As she was walking on top of the cobblestone path, she couldn't help but feel a heavy aura. The princess turned to look back, ready to summon her weapon but no one was there.

She continued to walk, only to hear the rustling of bushes. Selene turned, this time truly summoning her weapon, a long staff of pure silver adorned with a large amethyst gem at the end with a crescent motif.

"Show yourself! If you're planning to strike me down, you need to face me head on!" she challenged whatever being was stalking her. She then heard a faint evil laugh, but couldn't find the source. She looked around cautiously for the evil creature but nothing showed up.

The last thing she felt was something cold behind her back and a sharp, needle-like object stabbing through her neck.

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Helios and Selene were facing each other in the ring, preparing to summon their weapons. They circled one another like planets, calculating and predicting each others' up coming moves. They stared at each other intently, with the faint glow of their auras surrounding them.

On the sidelines, the bladers and bey spirits watched. Hyperion was looking at this two children worriedly.

"Helios, please be careful with your sister." Hyperion prayed in his heart.

"Ready...Set!"

"3!"

"2!"

"1!"

"Go...Shoot!"

The twins rushed towards each other. A fast pace fight ensued as sword and staff clashed with one another. The siblings spun, twirled and leaped around avoiding each other's attacks while their weapons struck ferociously.

When Selene was vulnerable, Helios prepared to attack, his sword bathed in blue flames.

"Volcano Strike!" Helios shouted as he drove his blade towards his sister. Selene acted fast, using her staff to create a shield and effectively blocking Helios' attack. She then twirled her staff and swung it towards her brother's head. Helios ducked down limbo style, successfully dodging the staff. Their weapons continued to clash.

"Your martial prowess is as strong as ever, Your Majesty. But even with that, you're not going to beat me." Selene said to Helios.

"Did she just call me 'Your Majesty'? Selene never calls me that, not even sarcastically!" Helios thought, sensing something off with the way his sister spoke.

Without realising it, Helios lost his focus. Selene took this opportunity and used her staff to knock her brother's sword off of his hand.

"You're wide open now!" she said as she aimed her staff towards her twin. An orb of white, purple and suspiciously, black began to form, ready to fire at Helios.

"Helios! Get out of there!" Hikaru shouted from the sidelines.

"CRESCENT BUSTER!" Selene shouted as a beam emitted from her moon staff.

The prince didn't have time to dodge. Before anyone knew it, Helios was engulfed by a blinding light. The others could only look on in shock.

"Woah...Helios got obliterated," Valt said.

"No...something's wrong." Eos mumbled worriedly.

The others heard her mumbling and turned to her. "What do you mean?" Hyuga asked.

"In all of the times my big brother and sister battled each other, Helios was always able to overwhelmed her quickly. Battles that Selene won lasted longer than the battles Helios won. He was just smarter and more agile. But here...Selene just beat him in a short time. Moreover, her fighting style looks more erratic. It just feels wrong to me for some reason."

This led the bey spirits to ponder. The more they did, the more they felt that something was not right.

Just as they were about to give their own thoughts on the situation...

"Hey, guys! Look!" Drum's voice called out to them. They instantly turned to the arena to see what was going on.

In the arena, Helios was still standing! He was holding up one arm, revealing a bright blue circle with a sun motif. He held it up like a shield.

"You've grown stronger it seems, sister," Helios said to his twin. "Tell me, was this the fruit of you and Shizuka's hard work, or were you two foolish enough to take a path of no return to obtain this power?"

Selene only glared at him. Helios had noticed that her eyes were a bit darker as well as hints of black in her usually white and violet flare.

"Not talking?" Helios sighed. "Fine, have it your way." he said coldly, his eyes glowing a menacing turquoise. Hundreds of blue fireballs appeared around Helios and flew towards Selene.

Selene put up a huge shield in front of herself. The impact between the fireballs and the shield caused the the entire training arena to shake and vibrate. The spirits sitting on the sidelines held the boys protectively in case the ceiling decided to collapse. Luckily, it did not.

Back to the twins, their weapons began to clash once more.

"To think that you are bold enough to attack your own sister like that." Selene said to Helios, her voice beginning to sound deep and raspy.

"Just because you're my sister doesn't mean I'll go easy on you," Helios said to Selene. "Especially for the fact that you just casted a killer move on me! Your own brother!"

Selene just chuckled. "I'm willing to sacrifice anything to surpass you. I will start with you, and then our dear father and sister, and last but not least, that little boy you so care about."

Just as Helios heard that, his sword once again lit up with flames of blue, this time even brighter than before. It emitted a heat so intense that even the others felt it. Selene backed away.

The twins' father watched as his children fought, realising the change in his daughter.
"Just as I have worried. Whatever happened to Selene that night had changed her." he thought.

As Helios' sword burned as bright as the sun, his hair flared up and five pairs of red wings appeared behind him. Eight blue rune circles formed around him, glowing with an intensity that rivalled Hyperion's bright flare. He glared at Selene with piercing eyes. For someone with the power of the sun, his gaze was as cold as deep space.

"Lay a finger on Hikaru. I dare you." Helios said in a threatening voice.

Selene didn't seem unfazed by this. In fact, she looked excited, a smile carved onto the princess's face while her eyes filled with unhinged ecstasy.

"Come then! I dare you to kill me!" Selene said as she charged up an orb on the moon staff. White pairs of wings appeared behind her, similar to the ones her siblings and father have.

The others could only watch in horror as the twins were literally about to kill each other.

"W-We need to stop them!" Aiga said frantically.

"It's too late!" Eos screamed.

"LIMIT BREAK: VOLCANO!!!" the circles around Helios as well as his sword shot out a huge blast of blue fire towards his opponent.

"CRESCENT BUSTER!!!" Selene released her special move once more.

The two energies collided, creating a massive shockwave. The blast should've blown the entire room apart, but Hyperion created a barrier to contain the explosion. It felt like the whole castle was caught in an earthquake.

The energy that that the twins created pushed against each other ferociously, fighting to overpower one another. Selene's attack was pushing Helios' flames back. Helios struggled with all of his might to fight the dark energy.

Helios knew that he needed to win. Not because of power, but because of the fact that his twin had possibly been caught up in some dark resonance crap and was now trying to kill him. Not to mention that she threatened to kill not only her own family, but also some innocent human kids.

From the sidelines, the others could only watch helplessly. They didn't know what to do to stop the twins. If they were to enter the battle, they would certainly get killed, leaving their masters vulnerable to a murderous Selene.

Hikaru on the other hand looked on as his partner struggled. "Come on, Hikaru, think! You can't just let Helios lose." he thought to himself. That was until, he remembered Dragon's words, back when they were attacked by Fenrir.
.
.
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"What Drum said was right!"
"He's no ordinary person. He and I have a connection that is the root our strength!"
.
.
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Hikaru finally knew what he had to do.

"Helios!" Hikaru shouted into the arena, catching the attention of his partner and his friends. "You can't give up now! I believe in you!"

The others watched in awe as a blue aura began to surround Hikaru.

"It must be hard doing all of this on your own. Let's do this the way we've always been doing!"

With that, Hikaru's hair flared up in a blaze of blue, his aura burning as bright as his partner's.

In the arena, Helios suddenly felt a strength unlike any other. It took him a second to realise that he and Hikaru were resonating with each other. He wasted no time and used this strength to push way Selene's energy beam.

Selene on the other side tried to counter this, but ultimately failed. She let out a scream before being engulfed by the flames. This impact created a blinding blast and later, a smoky aftermath.

Hyperion deactivated the barrier he put up and immediately ran into the ring. The other bey spirits followed him, leaving the boys on the sidelines.

"Helios!" he cried out for his son.

When they reached the arena, they saw the blue-haired spirit. He was panting and sweating, but despite all of that, still managed to stand up straight. His hair had gone back to normal and his wings had disappeared.

"Helios! Are you alright?" Valkyrie asked.

"What happened back there? Why did you and big sister decided to kill each other?!" Eos questioned her brother worriedly.

"It looked...like she... went down...a dark path..." Helios said between breathes. "She-"

"I'M NOT DONE WITH YOU!" a blood-curdling voice shouted, interrupting the prince.

They all turned to the direction of the voice only to see a beaten up Selene rushing and screaming towards the group with full speed in a blinding rage.

"She's still kicking!?" the boys thought.

Selene was about to reach the group of bey spirits and possibly tear them apart, until suddenly, blue chains that appeared to be made out of water emerged behind her out of nowhere. The chains bind themselves around the mad princess, restraining her.

"My, my. A kind and tenacious princess like you attacking her own kin? How uncouth." a familiar voice followed after.

The boys and bey spirits turned to the voice. A certain redhead stood in their sights.

"Achilles!" they said out loud at the sight of the redhead's return. They noticed through seeing Achilles' hands that he was the one who restrained Selene.

"Oh, thank The Divine. You've returned from Phthia." Hyperion said.

"Now's not the time for cheesy greetings, King. You need to purify her quick!"

Hyperion was shocked at this suggestion but obliged anyway. He extended his hands towards his restrained daughter, making a bright circle appear below Selene's feet. When the circle was formed, Selene screamed in agony, like a devil at the recitation of prayers.

"It's alright, my daughter. Your pain will be temporary." Hyperion said, before saying some incantations.

The princess only screamed more at this. A thick, black liquid began to ooze out of her eyes, mouth and ears. Valt and Aiga covered the younger bladers' eyes at this horrifying sight.

The screams lasted for a few minutes before finally going silent. Selene dropped to the floor unconscious with a pool of the black liquid beneath her. Achilles released her from his chains.

Hyperion walked towards his daughter and lifted her unconscious form. He then turned to his companions.

"All of you. Keep watch of your masters. I will take Selene to her room." he said to them.

"May I help too?" Eos asked. Hyperion nodded in response. The father and daughter left the arena.

The others were still in shock of what just happened. As they were trying to process the situation, Helios kept staring at the black liquid that his twin just bled out.

"This black substance. Could it be the cause?"