Netherborne [An OP Monster Isekai]

"Yes, Princess." The knight replied with his hand resting on the hilt of a sheathed, rusted blade. "This is the end—the [Demon Lord] is here."

Luna Cloudhell stood rooted in place. The roar of the titanic monster that had emerged from the Grand Dungeon echoed through the valley as a red-scaled limb ending in three claws slashed through the coiling smoke and smashed down onto the street below.

Bells rang throughout the city as a constant reminder of the impending fate of the Frostlands. Luna felt a yearning to run back into the castle and spend her final moments with her father—but she paused. Her father had witnessed the death of his wife and son in recent months, and Luna didn't wish to let the old man see her death as well.

It's best to let him sleep his final moments away. Oblivious to the doom his daughter and people are facing.

Perhaps it was a selfish decision, but Luna didn't want to see him cry again. The once proud king had been reduced to a hollow husk with no life left to give.

With the Frostlands military and Delvers likely overwhelmed, Luna saw no hope anymore. A part of her wanted to fall to her knees and break down in tears, but she held it in and addressed the waiting knight.

She stood at attention, putting her feet together, and bowed, "I thank the gracious knight for serving my kingdom throughout such terrible times. Henceforth, you are dismissed."

The knight smiled sadly and returned the bow, "My deepest thanks for your kindness, Princess." And with those words, he turned around and departed through the castle's gate with a melancholy look on his sunken face.

Luna bit her lip as the chaos continued in the distance. What should she do? The idea of running always festered in the back of her mind. There were secret tunnels in the castle that led away from the mountains, but they were in disrepair and unmapped. She also didn't fancy her chances of surviving a trek to Eshnar across the cursed forest with nothing but the clothes on her back and her mediocre talent in ice magic.

Her eyes drifted to the stone castle walls that had felt so safe and secure throughout all her life. But with them being desolate of guards and the castle gate wide open, Luna realized how fickle it all was.

Curious about how dire the situation was, Luna decided to climb up a winding staircase within the wall to the top. Every step felt like it could be her last as blood rushed around her ears.

Once on top, the breeze helped calm her quivering heart. The smell of flame and death tickled her nose, but she ignored it and enjoyed the scene. In the distance, she could see the Grand Dungeon's entrance overflowing with monsters. A sparse line of the Frostlands military was left fending off a dense wave of monsters that endlessly poured out.

The most numerous foes were the red-scale reptiles that were the size of a dog with a tail ending in a spiked ball and limbs that ended in claws. They should have been easy enough to deal with as they were known for populating the first couple of floors, but the soldiers were famished and exhausted, so they were hardly holding them back.

However, the most significant issues arose with the next wave of mobs, the golems. Not known for being outright aggressive unless provoked, the three-meter-tall humanoids of stone shook the ground as they lumbered forward with laborious steps.

Luna saw this destruction clearly as the Grand Dungeon's entrance was on elevated ground higher up the mountain. Screams of her citizens filled the evening air, and the smoke rose in columns as everything was set ablaze.

In the street below, a knight furiously fighting off two red lizards noticed their impending doom too late as a golem's thick arm hurtled and pulverized them into a paste.

Luna's eyes widened at the scene, and she hissed through clenched teeth, "Stop fighting and run you fools. It's all over." A tear ran down her cheek, "Stop dying... please."

The golem slowly lifted its arm, coated in a layer of blood and guts. Jagged pieces of the knight's metal armor slid off the stone arm and fell to the ground. The other knights nearby stumbled back with their quivering swords raised.

Luna was about to give up hope for the group of knights when someone new arrived in a blur. The woman ran up to the golem with nimble steps, and blue energy wrapped around her foot as she roundhouse kicked the lumbering giant square in the chest. Cracks appeared, and moments later, the golem crumpled to the ground alongside a shattered orb.

The woman, wearing leather armor, with blonde hair in a ponytail, whipped around a second too late to block a red lizard that lept up and clawed at her face, ripping out a chunk of her cheek in a shower of blood and then slamming its spiked tail into one of her legs.

Luna silently prayed for the Delver while watching the woman collapse to one leg. The Delver fell flat on her face as two more red lizards jumped onto her back with immense force. She rolled around on the floor, swinging an empowered dagger wildly.

Over the bells, screams, and chaos, Luna couldn't hear the last words the Delver yelled before her neck was slashed. Luna could only pray to the Goddess that the Delver had gone to a better place.

Luna placed her hands together and was about to pray for the deceased soul but then paused. The Goddess had forsaken them and turned a blind eye to the [Demon Lord], who had pushed her kingdom to the brink of destruction. How could she possibly pray to the Goddess in a time like this?

With the Delver dead, the lizards continued assaulting the group of knights holding down the street. The defensive line crumbled within seconds—they all lay dead by the wayside as hundreds of red lizards, some the size of adult men scampered over their corpses.

Luna's eyes went wide as she looked down the street with her hands mid-prayer. Not only was there a wave of monsters heading straight for her, but the boss monster that loomed over the city had picked up a building and was rearing its arm back with its eyes set in her general direction. Of course, it likely didn't help that Frostland's royal castle was the most conspicuous and tallest building in the entire city.

It was at this moment Luna realized something. It was one thing to know you would die soon and an entirely different feeling to be staring death in the face.

The imminent threat sent Luna into a panic. Her life flashed before her eyes as the clump of bricks came hurtling across the city directly at her. Luna closed her eyes as the debris cast a shadow over the castle. "Goodbye, father, I will be seeing mother soon—"

"Are you the ruler of this place?" A soft female voice asked.

Luna trembled. Had the Goddess made an appearance in her time of need? She opened her eyes and blinked in confusion at the girl floating a few meters away from the wall.

The girl's curious eyes were liquid gold, as were the blood vessels visible through the skin of her cheeks and neck. But why was her Goddess dressed in black armor from head to toe? And when Luna looked closer, she saw how the armor shimmered as if made from... mana?

"Goddess?" Luna felt dumb asking such a question but felt the need to confirm. The girl before her didn't match any of the depictions she had seen of the Goddess.

"What Goddess?" The girl mirrored her question, tilting her head, "I'm no Goddess... my name's Alice."

"Alice?" Luna's face fell as she searched her memories to see if any S-rank mages went by that name, but when she came up blank, she couldn't help but frown.

Removing all her curiosity about what had happened to the incoming pile of bricks, Luna asked seriously, "Esteemed mage Alice, why are you here?"

"Why am I here?" Alice chuckled, "To provide help, of course."

"Why?" Luna felt lost. Why would an S-rank mage bother saving such a backwater kingdom? Did the mage hope for payment or a noble title? Luna turned pale at the thought of her empty coffers without a single item worth selling. "I don't understand..."

"It's simple, really." Alice's smile sent a shiver down Luna's spine. "I obey the Demon Lord's orders."

Before Luna could even process what Alice had just said, the sky lit up as a flash of purple lightning shot across the city and slammed into the titanic red-scaled monster. For a brief moment, Luna thought she saw a tall, shadowy humanoid that towered over the buildings, but it was already gone. Had that been a figment of her imagination? Who shot the lightning...

"Wait, Demon Lord?!" Luna stumbled away from the castle walls edge. "You work for the Demon Lord? Why are you helping me? I don't understand!"

"Just stand there and watch. It will all be over soon." Alice proclaimed as black flames materialized in her hand. She then casually chucked the fire.

Luna watched a tiny ball of condensed black fire sail lazily through the air and land in the center of the lizard and golem horde. A second passed, and nothing happened, but then one of the lizards exploded into an inferno of hellish black flames that ate away at its skin, melting it alive.

The flames rapidly spread like a plague from one lizard to the next until the fire melted even the golems. Luna couldn't help but feel uneasy seeing a single spell kill hundreds of monsters, and Alice had made it look so effortless.

But then a shadowy mist appeared, obscuring the bloodied street. A voice that seemed to come from everywhere at once echoed like a chorus of the dead, "Rise my minions."

The dead bodies in the shadowy mist trembled as they stood up again. The air then shimmered as a shadowy being materialized, the same one Luna had seen only moments ago that she thought had shot the lightning. A cloak of shadows shrouded its towering form, and Luna caught sight of meter-long blades glinting in the light, and many golden eyes swirled among the darkness.

The creature was destruction incarnate, and Luna had no need to guess the creature's name as her system sprung to life and helpfully displayed it in bold red words floating ominously above its head:

[Demon Lord]

The [Demon Lord] spread his arms wide and decreed, "Secure the city. Conquer the Grand Dungeon. From now on, the Frostland is under my rule."

The monsters, which had been only moments away from eating Luna alive, roared in unison for their new master and charged toward the Grand Dungeon alongside a hoard of undead ogres and knights the Demon Lord had brought with him.

"And make sure to leave all the people alive." The [Demon Lord] called out after his forces.

Luna collapsed onto her arse and stared up at the smoke-filled sky. Why would he want to leave us alive? What horrific fate awaits us?