My Vampire Little Sister

Cthulhu.

A Demon Lord of mythical proportions. Many claim that once they laid eyes upon the horrific beast, they would lose all sense of reasoning. Their souls would be frozen, and their entire bodies would be rendered useless. And after seeing the enormous creature in person, I finally understood why.

Outer Demons were monsters that possessed unique sets of talents. They had enhanced bodies and increased magical capacity and often were monsters with supernatural powers beyond human capabilities.

And by that logic, a Demon Lord would be an extension of that. They were monstrosities that reigned over vast amounts of Outer Demons, utilising powers far beyond that of any regular living creature.

Alas, that logic was skewed.

When I look at Cthulhu now, I see a blob of natural energy. A deep ocean of magic power, and essence that took the form of a hideous creature. Demon Lords weren't enhanced Outer Demons… They were the spawn of the planet itself.

Just like the World Tree created Sora to act as its avatar, the Demon Realm created the Demon Lords to act on its behalf. They used the energy of their home planet to power their bottomless magic and enhanced physical state. To mere mortals, Demon Lords were akin to natural disasters. They could only pray to survive the hurricane once it passed and could do nothing to face its wrath.

Eyghon, being an automaton, was the only exception. No, given that it was a machine, it couldn't be described as a Demon Lord. What stood before me was a bona fide emperor of monsters.

"Brother… That's…"

Irina was shaking. Even after receiving my power-ups and training her Winter Sovereign Aspect, the girl could not shake off the primal fear that all mortals had when facing a force of nature. However, even though she was struck with a lethal dose of fear, the girl stuck by my side. She was willing to die fighting alongside me, then escape to safety.

That's the kind of little sister I had.

"Irina, do you trust me?" fre𝑒𝘸𝚎𝚋n૦ѵℯl.c𝒐𝘮

"B-Brother… Y-You can't mean!" Irina squinted her eyes as she looked at me. As expected, she could tell my intent just through those words alone. Smiling, I stroked her pretty hair and said:

"Help the Everwinter House clean up this mess, will you? I'll deal with this monster."

"B-But!"

"Don't worry about me," I turned my attention back to the octopus head, who was still dazed by my initial attack. "I defeated a Demon Lord before; taking another shouldn't be challenging."

"Brother…"

Irina was reluctant, but I firmly pushed her away, and she levitated down to the other members of the Everwinter House. Even though she would face Cthuhlu's goons, it was far safer than staying to challenge the Demon Lord. Besides, now that I've instinctively looked Cthulhu in the eye, I knew…

I can beat him.

"Grttttt…"

Cthulhu recovered from the dizziness from moving through a portal and the residue of my destructive lightning, only to let out a low, resonant growl. It looked straight at me as if I were the bane of its existence and the enemy of its kind. At the same time, I could sense a certain whiff of curiosity from its glare.

"So you're an intelligent creature, huh? Well, that's intriguing…"

Eyghon was a mindless machine that moved without its own will, so it was easy for me to kill it off. But against an intelligent creature… I'll have to improvise.

"Since you're the Matron of the Seas… Let's switch locations, shall we?"

I snapped my fingers and allowed the Spacetime ring to do its work. An azure light covered the Demon Lord and me, warping us through space and over a thousand miles away. The cold, wintry skies were replaced by a clear blue sky with a bright orange ball hanging above it all. The snowy white floor had disappeared, and in its place, dunes of yellowish-grey sand covered our feet. And finally… The cool and moist climate had become barren, dry air.

"#"

Cthulhu spoke in a language foreign to me, but I could tell it was confused. If I were in its shoes, I would be too. Given that we've been transported into a dry and arid landscape in less than a second.

"Yes, cry all you want. As a being of the ocean, I'm certain this desert is welcoming for you."

There was no way I would fight Cthulhu in the middle of the Everwinter House, where snow and ice were overabundant. And I couldn't transport it to any other common battlefield, given that water was bountiful throughout the planet. Therefore, to weaken the Demon Lord, I brought it to the only place it couldn't use the full extent of its powers.

"Mahayana Desert. It's not called the biggest desert on the planet for nothing. All you can find is sand and hot air for miles."

I scoffed at Cthulhu, who was still trying to recover its wits. And taking advantage of its lapse of judgement, I controlled my Soul Armament once more and conjured up the next surprise I had for the towering Demon Lord.

Boiling from beneath the beast, the desert sand bubbled out of control. The temperature rose dozens of times until the image of Cthulhu became fuzzy. Rainbow and crimson light conjoined together while magic power overflowed from my body.

"Genesis-Interitus: Muspelheim!!!"

And with a single explosion…

BOOOOMMMMM!!!

A scorching white light lifted itself from the pits of the desert and engulfed the Demon Lord with a searing hot flame. It burnt with the vengeance of the nine hells as tongues of deathly flames cooked Cthulhu from the outside. A harrowing scream escaped from the Demon Lord's mouth while its tentacles flailed about.

Hoho… So even Demon Lords feel pain.

I wonder if I burnt it long enough, I'd have enough octopus to make a lifetime's supply of takoyaki, perhaps even open a shop to sell that unlimited supply. But alas, my entrepreneurial ideas were cut short by Cthulhu's gut-wrenching roar.

"AWAAARRRRRRRRRR!!!"

Suddenly, a wave of mystical energy covered the Demon Lord and extinguished the flames before it could cause any more damage. At the same time, water erupted from Cthulhu's body, creating an artificial lake within the barren desert. Cthulhu ignored me entirely and dived to the lake's depths, seeming to recover its burnt body.

While I should have gone after the Demon Lord, my mind was still affixed to the mystical energy it used.

It could completely douse the flames of my magic, overriding my Progenitor's magic power within seconds. Only the magic power from a superior Progenitor could do that, yet… Cthulhu's mystical energy wasn't magic. It was eerily similar to…

"Holy magic."

Just like how the Holy Church used the Faith Dimension to draw their Holy powers, the Demon Lords of the Demon Realm did the same. Yes, Cthulhu itself was a bottomless pit of magic power granted life from its home planet, but at the same time, it had innumerable Outer Demons worshipping it. So, it made sense that it could draw on the Outer Demon's faith to heal itself.

My goodness, if the Holy Church knew it shared the same magic system as the Demon Lord… HAHA, I'm just thinking about it makes me laugh.

Now that I mention it, shouldn't I create my own Faith Dimension, then? If a Demon Lord like Cthulhu could use it, I don't see any reason why I couldn't. And the best way to garner Faith energy was with a display of strength. If I recorded myself burning a Demon Lord to death… wouldn't that make me the world's most admired person?

Yes, that sounds good! Sometimes, I frighten myself with my brilliance.

While I was busy setting up cameras and recording devices for my directorial debut, I'd forgotten one major problem…

"GRAAAAAAAARRRRRRRRR!!!"

Cthulhu emerged from the makeshift lake and flattened hundreds of sand dunes within seconds. Bits of charred skin fell down from the scaly monstrosity, but most of its burnt body had been healed.

"I guess a Demon Lord is still on another level. To recover from that attack so quickly… Not even I could do that."

My most powerful fire spell, Muspelheim, gathered the energy of over a hundred hydrogen bombs and concentrated them into one singular fiery attack. It had the power to melt mountains instantly and turn an ocean into a realm of endless fire and ash. To take that head on and come out unscathed… I guess Demon Lords really are on another level.

Well, not that it came without a cost.

"One-hundredth? Yeah, your energy has been depleted by one percent. If that's the case, I just have to hit you ninety-nine more times, right?"

My face naturally let out a sinister grin. Nothing could hide from my eyes, especially when learning the truth about lifeforms and magic. Cthulhu was from another planet, and all of its power was derived from the energy of the Demon Realm. Back in its homeland, it could quickly replenish what it had lost through simple absorption. Alas, we weren't in the Demon Realm, and I had the home-court advantage.

So, if I used Muspelheim ninety-nine more times… Cthulhu will naturally perish. I prepared my magic power to launch yet another spell. But before I could do that…

"... You're the one."

"Huh?"

A grimy, old voice sounded out inside my mind. I widened my eyes, naturally understanding where the voice came from. Instinctively, I stared straight into Cthulhu's yellow, demonic pupils and loudly asked:

"You speak our language?"

"..."

Cthulhu remained silent. It raised its arms skyward, and like an Aztec Priest praying to the weather Gods, it summoned a deluge. Dark clouds covered the desert sky, and heavy raindrops followed suit. Within seconds, the arid landscape had become overwhelmed with enough water to fill an entire ocean.

The Demon Lord indeed was a natural disaster. To summon rain beyond any hurricane I'd ever experienced and to turn the infamous Mahayana desert into a climate suited for a tropical rainforest.

Doused in gallons of cold water, Cthulhu's returned to its peak form and an undisguisable pressure mounted on my body. It felt like I was against an entire ocean, with all its energy concentrated in one spot.

But even though I was being pressured, I didn't falter. Instead, I stood tall and took Cthulhu's energy headfirst. And in response, the horrid being's mouth moved, letting out the same voice that once resonated in my head.

"Goddess… I've found him."