Elemental Hero in Teyvat

As soon they all enter the Dvalin's Lair, Dvalin appears in front of them as Stromterror began eyeing towards Sekai.

Dvalin: Elemental Hero, this is not your place to meddle with!

Then a sudden gale blast Sekai away towards the exit.

Aether: Sekai!!!

Aether rush towards Sekai activate his glider as he grabs Sekai's arm.

Sekai: Thanks for the save, but you do remember I can just summon my hoverboard right?

Aether: Ahahha… heat of the moment…

The Silver Adventurer changes to cyclone element and summon his hoverboard.

Sekai: Spinning Vertical Wind…

Wind begun to surround Aether, Diluc and Jean. They began to levitate from ground.

 Aether: This going to be handy… thanks Sekai!

Soon their conversation was cut short when Dvalin come out and flies away. Seeing this both Sekai and Aether give a quick chase after the dragon.

As Aether begun blasting Dvalin with wind projectiles attack Sekai joint him by enhancing each Aether blast with cyclone element. But the dragon was moving around a lot making it hard for the two to hit him.

Sekai: This start to be annoying… Sekai double split!

Suddenly bright light engulfs Sekai as the light split into two, showing two Sekai. One with white jacket and another with light blue.

Aether: What?! H—

Sekai: Let focus on this fight, I'll explain after this. Just trust me!

Sekai (solar) solar leap behind the dragon back. As soon he landed, he sees two purple crystal that was currently implanted on Dvalin. He smirks and start summoning Solar Blade.

Sekai (solar): Let's get this party started!

Sekai (solar) quickly rushes at the giant crystal on the dragon back and began hack & slash it. As soon he manages to destroy one crystal he continues to deal damage on dragon back towards second crystal. From range, Sekai (cyclone) and Aether continue to bombard Dvalin providing cover fire and distraction for Sekai (solar).

Dvalin howl in pain due to Sekai continuously assault on it back for a few times before finishing it off with Solar Blade shot towards the crystal making a small crack. The dragon roared in agony before losing its strength and begun falling to the platform. Dvalin growl in pain try to raise again but Diluc, Jean and Venti take this chance to charge at the dragon to deal damage towards the crystal.

But the dragon manages to wake up after a while and manage to send claw swipe towards them, knocking them of Dvalin, but Sekai(solar) manages to stop Dvalin rampage by blasting Solar Beam Blast towards Dvalin hitting Dvalin torso as the beast turned around and see Sekai(solar) pointing Solar Blade and ready to unleash Solar Blade Wave.

Dvalin roared at Silver-hair adventurer and tries to maul him, but he parried the attack and performed overslash towards giant dragon. Sekai(solar) quickly Solar Leap away and send multiple of Solar Blade Slash at the dragon.

However, it only manages to enrage the beast even further making Dvalin swipes away the Blade wave while sending back a wind blast towards him. Then, Dvalin rush towards him to give a bite. But Sekai(cyclone) manages to help by sending multiple Cyclone Disk to Dvalin's face making it howl and stop it attack.

Just when Sekai(solar) manages to land on platform, Dvalin went frenzy and start to create energy blast on it mouth and blast towards Sekai(solar) direction. Caught off guard, Sekai(solar) was blast into a few pillars knocking him off. Dvalin see this continue his assault and dash towards Sekai(solar) to end his life.

Sekai(solar) manages to get up and instantly Solar leap away from Dvalin tackle. He didn't manage to time his landing letting him crash beside Venti but still having smirk on his face.

Sekai (Cyclone): Let's finish this, Aether!

A deafening hum of wind surged through the air, the pressure distorting the very space around them.

Aether & Sekai (Cyclone): Mega Cyclone Vortex Disc!!!

With synchronized movements, the two rushed from behind Dvalin, channeling the full force of their Anemo + Cyclone power. The combined attack struck the tainted crystal lodged in the dragon's back, shattering it completely. A burst of energy erupted from the impact, sending shockwaves rippling through the air and obliterating the crumbling platform beneath them.

As the structure collapsed, they all plummeted into freefall.

Sekai (Cyclone) gritted his teeth, summoning the last remnants of his wind to slow their descent, but exhaustion overtook him. His glowing form flickered, the swirling winds around him dissipating as he reverted back to his normal state.

Sekai: Damn… not now…

Gravity took hold as they plunged through the stormy skies, the city below rushing toward them.

Suddenly huge things flew around them, saving them from falling into abyss...

When Sekai wakes up, He found up that he and everyone else on top of Dvalin, flying above white cloud. Venti stroke Dvalin's back.

Venti: It's been a while since we flew like this together huh, Dvalin?

Dvalin: Just now… why… why did you not ask me to protect you like last time?

Venti: Me not wanting you to listen to Abyss Order doesn't mean that you have listen to me.

Venti sits down and balance his body and continue,

Venti: Freedom if demand of you by God is no freedom at all.

Venti uses his power to create Anemo ball and transfer it to Dvalin.

Dvalin: Is this… the power of Anemo Archon? But I'm no longer part of the four winds.

Venti: Even if that so, you still protect us regardless. Now spread your wings of freedom and go with my blessing.

Then Venti heard a small clap.

Paimon: Waaa…. That's so sad!!

Paimon sniff and hug Aether's arm. Sekai only sits down and cross his arms with his eye closed. Jean looks at them and ask

Jean: Um… so what actually happen at that last moment? I mean Sekai split into two and go on attacking Dvalin, then…

Sekai: (sigh) let just say I can clone myself into two… I don't know how to explain it any simpler way. As for how Aether does that last attack. Aether can you please…

Sekai suddenly falls back to laid on Dvalin back. He feels exhausted is reaching him. Aether sees this just look at him with smile and start explaining what happen.

-Small Flashback-

Sekai (Cyclone): I know you are confused right now but hear my plan. We will help giving cover fire to the other me. Then try to get Dvalin attention. The other me will try to destroy the final crystal colt on that time. If he didn't manage to destroy it. It will fell on us to destroy it. It like we tagging between us, but this time with bigger target.

Aether: That kind of simple and effective method. But how do you want me to destroy that crystal colt, I didn't think my wind blade enough to destroy it, if even your Solar Beam Strike only manage to leave small crack.

Sekai: I'll help you when that time come. But now, time to role!!

The first plan didn't run smoothly as they thought, as Sekai (cyclone) instruct Aether to start casting Palm Vortex. After done helping his other self, he dashes towards Aether and put his palm on top of Aether.

Sekai: Focus Aether!

Aether starts to feel that anemo elemental energy start accumulate faster and faster. He can hear the anemo telling him to save Dvalin. He also can feel how cyclone elemental energy start to enveloping his Wind Vortex and know how powerful his element energy is. It's so pure that it enhances Traveller Anemo energy on that moment.

Aether than look at Sekai with surprise, while he just making a small smile towards him and spoke.

Sekai (Cyclone): Lets finish this, Aether!!!

Then everything happens as what they know, the platform broke because of the power impact making they all fall and been saved by Dvalin. 

 After Aether finish his explanation, everyone else have a look of shock towards sleeping Sekai.

Jean: I though he uses Anemo element, I don't know he is using different element. And a higher tier Anemo element is the thing?!

Diluc: Calm down Jean, I know this is surprising, but everyone has their own secrete. And especially him… you should respect that.

Jean: Ehem… sorry I just surprise.

Venti: (muttering) Afterall he is that elemental hero…

-And so, the Stormterror threat was quelled-