“Welcome home, Sister!” Amilie yelled. “Let’s play!”

“No! You don’t even know what playing is!” Cailie answered.

“No? No?! Who are you to tell me no! You are just a useless, worthless nobody!”

“No.” Cailie said calmly. “That is who I used to be. Now I am much more.”

“No! You! Are! Not!” Amilie yelled, as she swung the arm that was holding her whip.

 

The whip reacted, shooting towards Cailie, but it never made contact with her, as Cailie used Spirit Magic to make a compressed wall of water between her and the whip.

… what? You didn’t know that Cailie could do that? Well, she is half spirit and she does have the spirit magic skill. In fact, she is probably better at spirit magic than I am. And the thing is, she also has the Instant Cast skill so she can use Spirit Magic without a chant. 

 

“W-What?” Amilie seemed taken back by the fact that her attack didn’t connect.

“You heard me. I am not the same. … but neither are you. Tell me, what happened to my sister? I know she wasn’t always the best, but at least you really cared about the clan. And now, you are just throwing them out. Why?”

“Because they are worthless! Just like you!”

“... I see.” Cailie said. “Then you, my sister, are no longer worthy of leading this clan.”

“And what will you do about it?! Challenge me to a duel?!”

“Yes, I will.” Cailie said. “You can’t be left in charge, so I’ll challenge you.”

“He, he, he, he.” Amilie once again laughed with her extremely fake sounding laugh. “Perfect. Then we shall have a duel to the death. And I’ll finally be able to kill you without those fools stopping me! Now! Let me take us to the place worthy of our final battle!” She called out, as she raised her left arm into the air … well water technically. The dungeon terminal on her arm shone brightly and in a flash, we had been teleported somewhere.

 

---

 

When we came to, we were in some sort of cavern. The cavern was only about half filled with water, leaving the top half of the cavern filled with air.

I quickly lifted myself out of the water to get a better look at the surroundings and took stock of who were here. Other than our group of four, all of the merfolk warriors were here, as well as Amilie. Daedelus didn’t seemingly teleport with us, but he was still summoned, so he must still be outside.

As for the room itself, it didn’t take me long to realize where we were. Because at the very center of the room was a pedestal I’m quite familiar with. A dungeon core pedestal. But the core on the dungeon pedestal wasn’t a core at all. 

It wasn’t round, like monster cores usually are. But more than that, it was moving. Or to be more accurate, it was beating. Like a heart. And that is because it is a heart.

 

“A dragon’s heart.” Lady Janina told me. “It isn’t commonly known, but they can be used as the core for a dungeon. I’ve done my best to make sure no more are made, but I also didn’t want to destroy ones that already exist.”

“... Understandable. I suppose you could consider this entire dungeon the body of the dragon, right?”

“In a way, yes.”

“And considering how strong dragons are, a dragon heart, if it comes from an adult dragon, should be equal if not greater than an SS-rank core.”

“It is greater, because unlike the core, the dragon heart will grow. The core of this dungeon originates from an adolescent dragon that was just reaching his adulthood. But now, with all the time it has spent as the core of this dungeon, that heart is stronger than the one that beats in Agunan’s chest.”

“... did you know him? The dragon?”

“Yes. He was a water dragon from my early days of being the supreme dragon. … In fact, he is a great uncle to Prabhu Jala, part of the reason why Jala wants to defend this place.

The dragon died in a fight against a great ocean beast. The species doesn’t have a human name from what I know, as the one that ended him is the only one I’ve ever known. But it looked like a giant man, larger than your Exodia, covered in tentacles.”

“... that sounds a bit too much like Cthulhu for my liking.”

“Something from your world?” 

“Yeah. A horror story. A series of books written by Lovecraft, and later others. They tell of god-like entities that will destroy everything. One of them, arguably the most famous, is called Cthulhu. A giant, relatively humanoid looking creature that has tentacles coming out of its face.”

 

“... what happened to the monster?” I then asked.

“I led a group of dragons and we defeated it.” Lady Janina said. “... a few of us were injured so badly that they ended up passing. It was one of my greatest failures as the supreme dragon.”

“And the dungeon?” 

“Was revealed in the fighting. Jala’s grandfather decided that the heart of his brother would be used as a core for the dungeon, and he chose the merfolk to rule it.”

“... I see.”

 

“... but something else is bothering me.” Lady Janina said. “... that mermaid. She has an abnormally large amount of miasma just hanging around her.”

I quickly activated Mana Vision and confirmed that there indeed was a lot of this blackened stuff around Amilie.

“... is that why she is so crazy?” I asked.

“Might be. I am more interested in how she got so much on her. I know the miasma levels have been on the rise, but they aren’t so high that the System cannot protect her from it.”

“There could be a minor fissure which is spewing out miasma.” I theorized. “Something the Goddess and the System Agents haven’t noticed. … or maybe she is somehow using the dungeon core to power up herself, but since the core uses both mana and miasma, she overloads herself with miasma and exceeds the System’s protection.”

“Perhaps. Let us watch and see.” Lady Janina said.

 

And just a moment later, a barrier formed from the dungeon core, pushing everyone except Cailie and Amilie to the outskirts of the room.

 

---

 

[Cailie POV]

 

After the shine, I found myself in the most sacred room for our clan. The core room of our dungeon. It was an important room in many ways. 

Members of the clan will be allowed to visit this room for the first time on their fifteenth birthday, after which they are given a ride by our guardian dragon, the great Prabhu Jala. 

But my sister never used to teleport here. We would always swim here, instead of this.

 

I quickly looked around and noticed that things weren’t correct in the core room.

The first thing I noticed was the mess. This room was always perfect. If it wasn’t, it would be cleaned until it was. It was a sacred duty of the one that held the position of dungeon master.

When I last came here, when I was banished, the room was still immaculate, but now, it looked like it had been the stage for a big battle or maybe many smaller ones, but that it hasn’t been cleaned after any of them.

 

And then there was a small outcove dug to the side of the room. It had a barrier in front of it, turning it into a prison. In it, I saw someone I really wish I didn’t have to see in the state he was. 

“... father.” I muttered quietly as I recognized the man.

“YES! Isn’t it perfect that he will get to see just how WORTHLESS you are?!” My sister yelled.

“... why?” I asked her, my voice calm, while in truth, I was boiling with anger.

“Why?! Why what?! He is worthless, just like you! We don’t need him, so he can spend the rest of his life there! Out of the way!”

“... is that really how you think? … what happened to you? I know you always hated me, but … you used to love the clan. You were the perfect leader. … but now, you are deranged.”

“Deranged? DERANGED!? Who! Are! You! To! Call! ME! DERANGED!” Amilie yelled. “Core! We are having a sacred duel! Make sure no one can interrupt!”

 

I watched as the dungeon core shone. It removed the others from the area, moving them to the outskirts of the room, before covering us in a magic barrier. The barrier would keep anyone from interfering, but it would also keep us from dying. And it won’t go down, not until one of us is left with 100 or less HP. The only other way is for one of us to admit defeat.

… I wonder if Brian could break it? He can, right? He has to be able to. And if he can’t, Lady Janina can. She is the supreme dragon, so she has to be able to, right?

 

No! I can’t focus on what Brian can do. I’ll focus on what I can do! And that is, taking down my sister and finding out where she went wrong!

 

“... our sacred duel. This is how it always should have been. No hallow prisons. No second chances.” My sister said, sounding calm for the first time since we met. “And this time, I will get rid of you. Permanently!”

“You may try!” I called back.

 

And with no further exchange of words, my sister charged at me. I knew she was at an advantage if I stayed in the water, so with a flick of my tail, I got myself some speed and pushed out of the water. 

Since I became a wind spirit, I’ve gotten somewhat used to Aerial Swimming. While I’m not as fast as Alice is with her Mana Flight, I can move through the air decently.

“Get back here!” My sister yelled, as she used two Water Whips in an attempt to bind me and get me back into water.

“No thanks. Wind Slash!” I quickly used a Wind Magic spell and cut both of my sister’s Water Whips. “Why don’t you show how superior you are and come up here?” I taunted a bit.

Taunting is important when fighting unstable opponents. That is what Brian taught me. If your opponent is angry, they are more predictable and easier to fight.

 

“Arrgh! Fine!” My sister seemingly fell for the taunt, as just moments later, a large bubble of water rose from the water floor and my sister was swimming in it. 

“Water Cannon!” She yelled, casting another spell, but it was honestly slow. The spells Alice uses move way faster, so it was an easy dodge.

“Wind Blow!” After dodging, I tried to counter with a spell of my own, but my sister dove into her water bubble and the water dissipated my attack.

 

“Ha, ha, ha! Even your magic is useless! Just like everything about you!” 

“Your magic isn’t doing anything either!” I called back. “How are you so superior when you can’t hit one useless target?!”

“Grrh! No more sisterly love! Water Kraken!” 

 

My sister’s next spell caused several tentacle-like appendages made of water to rise from the water below. They all then began to attack me.

I’ve heard of this spell many times. It is considered the sacred spell of our clan, because it was made to look like the great calamity that took away the brother of our original guardian dragon. The dragon whose heart was used for the core of our dungeon.

Not many of us can learn this spell, which is why the one that does is often named the leader of the clan. That is how my sister got the position.

 

It is a powerful spell, but I’ve dealt with worse. Ever since Brian got that Dark Chain skill, he has been using it in practice, so I’ve learned how to dodge these kinds of things. 

And no matter how powerful this spell might be, when cast by someone so much weaker than Brian, it just cannot match up to him.

 

“Wind, Rage to your heart's desire, Wind Storm!” I chanted a powerful AoE Wind spell and let it rip apart my sister’s spell. It even destroyed her Water Bubble, causing her to crash into the water below.

I then prepared to use another Wind Blow as soon as she surfaced, but what she did next wasn’t what I expected.

 

“Summon Water Spirit.” I just barely heard my sister using the skill while she was underwater.

I knew she had a blessing of an ocean spirit, one of the greater water spirits, but I never expected her to use it when in a sacred duel. This is a one-on-one duel. No outside interference. I assumed it also applied to summoning skills.

I pondered for a bit if I should use my own spirit summoning, but I didn’t have the time, as my sister burst out of the water, with a dark sinister aura surrounding her. She then gathered a lot of water, forming a humanoid water form around her.  It was made with the Water Avatar spell.

“Ha, Ha, Ha! I’ll show you just how weak you are! You’ll never defeat me now!” Amilie cackled.

Did she synchronize with a spirit? She must have. I might have to do so as well.

 

“Cailie! That isn’t a spirit!” I heard Brian calling from outside the barrier. “It is a sprite!”

A sprite? A corrupted spirit? That might be why my sister is … worse than before.

I need to take it down.

“Mom. I need your help.” I said quietly, before looking up at my sister and the sprite she had synchronized with. “Summon Wind Spirit!”