Everything happened all at once.

Susie was the first to attack. She charged towards Queen Susan, axe raised over her head, when her legs suddenly collapsed and she became pinned to the ground by a black and white Delta Rune symbol. Ralsei waved his hand, summoning a wave of purple and white light to enshroud Susie, releasing her from the spell. Susie was quick to get back onto her feet in time to deflect a blow from the King's chain.

Kris's sword met a barrage of words from the Queen's spinning pen, blasting them with enough force to push them back onto the altar. The Queen wasted no time to charge towards them, spinning so fast that her body was just a dark grey blur. A wave of fire from Ralsei blocked her advance, but instead of stopping, she jumped into the air and barrelled down towards him.

Susie was already by Ralsei's side, sending the Queen a menacing swipe of her axe. As she warded the Queen off, she spun around and deflected the King's chain. Ralsei followed up by blasting both the King and Queen with a massive fireball.

The fireball fell against a wall of black-and-white magic and faded into nothing.

Kris dashed down from the altar and tried to stab Deltarune. Their other self turned around and, with a self-confident smirk, threw another black and white Delta Rune towards them. But Kris only felt the shackles of that spell for a moment on their limbs before it faded away. Deltarune staggered back as a ring of fire surrounded themselves, with an opening for Kris to charge through. Before Deltarune could run away to safety, Kris sprinted through the opening, sword aimed at Deltarune's neck.

The fires dissipated as Deltarune summoned up a swarm of black and white magic. Kris felt a spike of pain course through their body as a bolt of black lightning burst through them.

Ralsei was ready with another attack. He raised his right hand and sent a rain of fire falling towards Deltarune from the ceiling. Then he pointed his left hand at Deltarune and shot a superheated, spinning orange ball at them.

The Queen struck at Ralsei again with her pen, only to be countered with a blow from Susie. However, Susie's hands were suddenly tied together as the King's chain wrapped around her wrists. She kicked out at the Queen and jumped backward, attempting to free herself from the chains. With a greedy laugh, the King swung his chain to the side, hurling Susie through the air and smashing her against the wall. She howled in pain as she slid to the ground.

Ralsei clasped both hands together and formed a wall of fire in front of himself to halt the Queen's advance. To his shock, she spun through the wall, setting her entire body on fire. The large pen on her shoulder began firing flaming words towards him.

Kris was busy dodging bolts of lightning when Ralsei's rain of fire struck Deltarune, temporarily disabling all of their magic. The spinning orange ball then hurtled into Deltarune's back, causing their black robes to combust into flames. Kris didn't let them have a chance to recover before they plunged their sword through their chest–

Only to stop inches away from their target as a chain wrapped around their sword and pulled it to the ground. With a gasp, Kris struggled against the King's mighty strength to rid their sword of their chain.

Ralsei jumped away from the Queen's fiery words, then shot a fireball towards her. Covered in flames, she was spinning a bit too chaotically to orient herself and was struck square in the shoulder by the fireball. Her pen fell off her body as she collapsed to the ground, smouldering.

Susie struggled back onto her feet, grabbed her axe, and charged at the King. When the King saw her coming, he let go of Kris's sword and fired his chain at her.

Kris lifted their sword back up in time to block a blast of dark magic from Deltarune. Immediately after, Kris's body crashed to the floor as a black and white Delta Rune symbol materialized above their head, preventing them from moving a finger.

Deltarune shook off their burning black robe, revealing a bright green cape that was shaped just like Kris's magenta one. From the sheath at their waist, they pulled out their own sword, a razor-edged black one teeming with bolts of black electricity.

Susie had deflected the King's chain and lunged for his throat. The King blocked her axe in time, but the ferocity of her blow sent him staggering backwards. She swung her axe again, gashing him across the shoulder. With a roar of pain, he attempted to jump forward and bite her with the second mouth on his belly, but she was too fast. She evaded his blow and kicked him off his feet, sending him sprawling to the ground.

Ralsei conjured up a dome of fire to surround the Queen before she could get back up and start spinning again. A panicked expression came over his face when he noticed Kris lying on the ground, paralyzed by Deltarune's magic. He swiftly waved his hand at Kris, shrouding them in purple light that freed them from the overpowering spell.

Deltarune stepped towards Kris, dark sword raised. Kris jumped back onto their feet in time to meet them with their own sword.

Susie slammed her foot down onto the King's chest, eliciting another groan of pain from him. Before he could use his chain again, she slashed it into pieces with her axe.

With the Queen and King both immobilized, Susie and Ralsei turned their attention towards Deltarune.

"It's three against one," Ralsei said. "Just stop, please. We don't want to fight anymore."

"Or you can keep fighting," Susie shouted, bloodlust in her eyes as she brandished her axe. "If you want to lose your head!"

Deltarune gave the two of them a dismissive look.

Kris took advantage of this moment to sprint towards Deltarune.

Their swords clashed in mid-air with a force that surprised both of them. Kris stepped back and was met with another blow from Deltarune's razor-edged blade that nearly sent their own sword flying out of their hands. Tightening their grip, they struck again, but this time, their blow was effortlessly deflected. Deltarune's swordplay was much faster and much cleaner than theirs.

Susie charged at Deltarune, but missed their neck with her axe as they ducked. Deltarune darted back, narrowly dodging another slash from Kris. However, Ralsei was already behind them, hurling a spinning ball of flames. Deltarune leaped out of the way,and the fire incinerated their cape.

Kris raised their sword in the air and was pleasantly surprised by the spiral of fire that materialized around the blade, courtesy of Ralsei. They lashed out at Deltarune, their swords clashing together blow after blow, each trying their utmost to find an opening in the others defences. Susie hurled herself at Deltarune and caught them in the hip with the hilt of her axe. With a shriek, Deltarune kneed her in the belly, throwing her body to the ground. A blast of fire then caught them on the shoulder, and Kris followed up with a stab straight at their neck.

Blood flew into the air.

Somehow, Deltarune came out of both attacks intact, but blood was now streaming down their face and neck. To Kris and Ralsei's surprise, the smile on their face only grew wider.

"I'll take care of this," Ralsei said, clasping his hands together. "Kris, stand back!"

"O–Okay."

The power that Kris felt surging from Ralsei was unlike anything they had ever experienced before. At once, the room began to shake, as if smitten by an earthquake.

Rocks fell from the ceiling, leaving clouds of dust in the air.

Jets of water burst out from the sphere of light hovering above the altar. Streaming around each other like snakes, they formed a massive whirlpool floating near the ceiling. A pillar of fire shot out from Ralsei's hand and struck the whirlpool, boiling the water and filling the room with steam. Blue and red encircled each other, creating spirals of fire and water, all of which coalesced into a flaming tidal wave that crashed down at Deltarune.

The impact caused the walls of the room to shatter and the floor to split into multiple pieces.

Kris, Susie, and Ralsei each grabbed onto the altar as the walls crumbled and the floor gave away. The site of the tsunami's impact had created an enormous, steaming crater. They could no longer feel the ground as the crater expanded and the floor caved in. Within seconds, the altar that they held onto had become a tower of rock that stretched up fifteen or twenty feet above the new ground level.

Yet, when all the smoke had cleared, Deltarune was still standing. Their cape was gone, and their body was covered in blood and burns.

Their eyes were glowing with vicious satisfaction.

Kris felt a chill go down their spine as Deltarune's lips curved into another smile.

"A million monster Souls won't equal the power of my human Soul," Deltarune began to speak. "So, Ralsei, what will you do when I crush you like the little bug you are?"

The magic surrounding their hand began creating another earthquake.

"The old scientist who experimented on me had a particular phrase he loved to say: 'I can do anything!'"

A sphere of dark magic erupted outwards from Deltarune's body.

Kris's head was suddenly filled with searing, unbearable pain. Every nerve in their body seemed to be screaming. Every fibre of their being was shouting for the pain to stop, for the suffering to end. Waves and waves of pure, undiluted agony was coursing through them, ripping apart their skin, tearing their muscles, shredding their veins, shattering their bones. It was an endless, blistering torment.

"Or how about this? 'Chaos, chaos!'"

Orbs of darkness, each crackling with webs of black lightning, fanned out across the room and encircled the altar. All Kris saw through their unspeakable agony was a flash of light, and then the altar was completely destroyed. Their bodies hung like rag dolls in the air.

"You should never have resisted. Now, the Fountain's power is mine, and all of you – all Darkners and Lightners, the King and Queen, all humans and all monsters – all life itself shall bend the knee to me."

Kris couldn't take the pain any longer. Their vision went white. Sound faded from their ears, along with all their other senses.

The world was receding, replaced by numbing darkness.

"Kris?"

"Mmm-hwa?"

"Hi, Kris! You're my baby sibling, and I'm your new brother!"

"rah...thur?"

"Yep. As your brother, I'll be taking care of you from now on! My name's Asriel, by the way."

"Ah...real?"

"As-riel."

"Az...ree...ul?"

"Hey, you're getting it! Good job, Kris. I'm so proud of you."

"Ku...ree...s?"

"Yeah, that's your name, Kris. We're going to have so much fun together!"

"Ku..rees...Az...reeal...brah...thur..."

"Wow! You're learning how to speak really quickly. Maybe you'll be able to talk in just a few months!"

Another voice.

"Asriel, baby Kris needs to sleep, so could you leave them alone right now?"

"Awww! But mom, I want to play with them a bit more..."

"No 'but's, Asriel. Go and play in your room by yourself for a little while, okay?"

"Okay, mom..."

Two fluffy faces looked down at them, smiling.

They felt fluffy arms lifting them up, cradling them, gently rocking them back and forth.

A voice was singing a soft lullaby.

"...light..."

"...shining..."

"...journey..."

"...everything..."

"...still..."

"...hearts..."

What were the words she was singing?

Kris strained harder to here.

But they had only been a baby. They couldn't possibly have understood the words she had been singing.

Yet, the words were so familiar...

Those fading words...

The lyrics of a lullaby...

Kris's eyes burst open.

The world flooded back into their senses, along with a surge of aches that made them wish they hadn't woken up.

"Kris! You're okay!"

Kris's vision cleared, and they saw Ralsei's face staring down at them.

That unbearable pain, that flesh-rending agony – it was gone.

"I'm...alive?" Kris spoke.

"Yes, Kris, you are alive! But you have to get up. You have to keep fighting!"

Kris lifted their head and looked around.

Deltarune stood upon a precipice, sword in hand, attempting to fend off five Head Hathys that were each taking swipes at them.

Bodies of other monsters lay strewn around the room. But what Kris hadn't expected to see was the hundreds – no, thousands – of monsters that were climbing up the precipice, climbing up to fight Deltarune, even as one after another of their brethren were being kicked off to their deaths in the crater below.

Rudinns, Hathys, Jigsawry, Ponmen, Rabbicks, Bloxers, Rudinn Rangers, Head Hathys, Clovers, King Rounds, and countless others that Kris had never seen before.

The whole room was filled with monsters streaming in, all charging towards the tower of rock at the centre to fight Deltarune.

"We Darkners will never bow to a human like you!"

Their battle cries filled the air as they helped each other up from the ground and walked fearlessly into death's maw together.

A motorcycle-riding Lancer and a reluctant Rouxls Kaard were already at the forefront of the next wave that had climbed to the top of the tower, rousing all the monsters together to make another charge.

"After Deltarune took the power of the Fountain, all the water in the world ceased flowing," Ralsei explained. "The Darkners in Castle Town and those in the King's army realized that without the Fountains, they were all going to die regardless of which side they fought on. So, they all banded together to attack Deltarune."

Then, to Kris's amazement and joy, Susie stepped into view. She was bruised and bloodied, but a smile still adorned her face.

"Deltarune underestimated us monsters," she said, grinning. "They thought they were so much more powerful than us because of their human Soul. But what d'ya know? When monsters get determined, we can kick some human ass together! Errhh, I don't mean yours, Kris. I hope."

Kris smiled.

Tears welled up into their eyes.

Everyone had come out to help them.

"Our battle isn't over yet, though," Susie said, tugging on Kris's arm to pull them back onto their feet. "Deltarune's magic is still too powerful."

"We have to try something else," Ralsei said, lowering his voice. "But this might just work."

"Tell us your plan," Kris whispered back.

Ralsei whispered his plan to Kris and Susie, and they nodded.

"All right," Kris said. "Susie and I will get into position. When we're all ready, give us your signal."

"Okay."

"Let's go!" Susie called.

At once, Kris and Susie darted off in different directions. Kris sprinted in a curve to the north and west from Ralsei, while Susie dashed northeast. Ralsei remained standing where he was.

Kris watched as the legions of monsters climbing onto the rock to fight Deltarune were thrown off, one after another, by barrages of dark magic and black lightning. Their bodies crashed lifelessly into the crater below. Only the return of the Fountains could save them. Kris felt desperate energy rushing through their veins, adrenaline saturating their blood. Losing to Deltarune was not an option.

When Kris and Susie both stood at their prescribed locations, they turned to face Ralsei, who hastily waved his hand up in the air.

Gleaming streams of white and purple light materialized around their three bodies. The Delta Rune symbol hovered above their heads, the two wings glittering. Kris waited for the moment that would decide the fate of all Darkners and Lightners.

Their feet was suddenly lifted off the ground, creating the sensation that they'd become weightless. In the distance, Susie floated up into the air with a puzzled expression on her face. Ralsei held his hand up, maintaining concentration as the spell he cast let them fly up to the rock that Deltarune stood upon.

Once they came into Deltarune's line of sight, they would only have a few seconds to achieve what they needed to do.

Kris held their breath, waiting for the moment they surfaced above the rock. They could hear their own heartbeat thudding while sweat dripped down their forehead. Their fingers trembled as they held their sword.

This was it. They were going to execute Ralsei's most desperate strategy.

Delta Rune Encirclement.

Kris floated up and over the rock, Deltarune coming into sight. Piles of monster bodies surrounded them, incapacitated Bloxers and Rudinns and Hathys all stacked up like columns of death. Dozens more were still fighting.

"Darkners of Castle Town!" Ralsei shouted as he flew above the rock. "Triangle Encirclement Formation!"

In an instant, all the heads on the battlefield turned towards Ralsei. About half of the monsters that were still conscious suddenly stopped fighting and began running towards the edges of the rock.

Chaos on the battlefield transformed into order as the monsters that understood Ralsei's command dashed into three lines that enclosed Deltarune in a roughly triangular space. Deltarune was quick to notice, however, and they charged towards one of the lines in an attempt to break through. The other monsters hurled themselves at them to stop their charge, but they were blasted away one after another by bolts of dark lightning.

Kris descended upon the rock, whereupon the Delta Rune wings that had let them fly disappeared. They sprinted towards Deltarune, sword raised.

Moments before Deltarune broke through the line, Kris met them with a slash of steel. Deltarune deflected the blow with ease, but took a step back to allow themselves space. Kris didn't let this moment go to waste and pressed forward with another cut. Their blade met fierce resistance as it fell into one of the jagged valleys of Deltarune's sword.

Kris had to hold their ground as Deltarune landed a kick against their shin. Biting back the pain, they slashed at Deltarune again.

During the few seconds afforded by this duel, the three lines surrounding Deltarune solidified, completing the first phase of the encirclement.

"Trident Attack Formation!" Ralsei shouted next.

A group of monsters at one tip of the triangle stepped forward and split themselves up into three smaller, triangular-shaped formations. The three formations arrayed themselves into a line with the two on the sides facing forward at Deltarune and the one in the centre facing backwards.

Kris couldn't keep up with Deltarune's swordplay any longer. They were being backed up against the outer line by their persistent flurries of blows. Summoning up the last of their strength, Kris took a step back and catapulted their body forward in an attempt to break past Deltarune's deadly blade.

They were stopped dead in their charge by a hand that plunged against their throat, knocking the air out of their lungs. The hand constricted, choking them, then lifted their entire body up into the air.

"Pathetic," Deltarune said. "This is all the resistance you can show me?"

Kris kicked and struggled as white and black spots flashed across their visual field. Their lungs cried out for air. Every muscle in their body was fighting, straining, begging to be released from the choke hold, but to no avail. Deltarune's lips curved into a victorious smirk.

Their arm started to go limp.

"Kris!"

Susie barrelled into Deltarune, knocking all three of them to the ground as she headbutted them in the side. A furious expression fell over Deltarune's face as they realized what they had just let happen. On the ground, Susie pushed her body up onto her knees and landed punch after punch against Deltarune, a desperate attack to inflict as much damage onto them as she could before she was thrown off.

Deltarune caught one of her punches in midair and twisted her wrist, creating a face of unspeakable pain. Before she could even scream, a blast of dark lightning flung her body so far back that she crashed against the outer line.

"Susie!"

Kris had no time to react before Deltarune was back on their feet, sword aimed at their head.

A blast of fire temporarily stole Deltarune's attention, giving Kris the split second they needed to grab their sword and reenter the duel with Deltarune.

With each blow they exchanged, Kris felt the raw demonic force of an inhuman presence. The opponent that they faced was no mere human, nor were they a monster. The power they exuded could be both seen and felt. An aura of chaos, an insatiable lust to hurt and to destroy, an overwhelming power that could overturn anything that stood in its way, send the whole world revolving.

Their other self smiled as Kris was backed up against the line once more.

"Here, Kris!"

The next moment Kris went in for an attack, fire coated their blade. Their sword smashed into Deltarune's jagged blade, sending a flurry of sparks up in the air.

Fire and electricity arced against each other, a tango that created spirals of destructive magic that coalesced into a whirling storm of carnage. Their two swords exploded, flinging both of them to the ground and turning the floor where they had formerly stood into smouldering red rock.

Neither had any weapon left to use.

Deltarune stared at Ralsei with a murderous look in their eyes.

"No, you're dealing with me!"

Kris hurled their body on top of Deltarune.

The next thing they registered was a ceaseless flurry of blows, both to and from their body. They could no longer tell who was screaming, who was trying to hit whom, or where the pain was even coming from. All they knew was they had to keep attacking to survive. They sent punches, grabs, kicks, bites, scratches, and received an equal number in return. They attacked like there was no tomorrow.

Unbearable agony shot through every vein in their body as dark lightning coursed across their skin. The fighting came to a stop with Deltarune towering over them, their hand buried against their neck. The world burned.

Kris's pain ended as quickly as it came as Deltarune was blasted off of them by a multi-coloured attack that looked like the simultaneous beam of every Darkner monster's attack at once. The awe-inspiring blast hurtled Deltarune back to the centre of the encirclement, their body crashing hard enough against the rock to create cracks.

"Kris!" Ralsei shouted, rushing towards them. "Are you okay?"

"D–Don't worry about me," Kris said, trying to smile through their pain and fatigue. "Just stop Deltarune."

Ralsei nodded with a heavy expression. "I need you to get back up."

Kris tried to climb back onto their feet even as every cell in their body seemed to be screaming for relief. Ralsei cast a healing spell over them, relieving some of the pain, but not by much. Tears came into his eyes.

They turned towards Deltarune, who was already about to get back up.

"We need to cast the spell," Ralsei said, wiping his tears away. "Now."

"I know."

"When I give the signal, you'll do what I told you, right?" A small blush came over Ralsei's face.

"Yes. I promise, Ralsei."

"Thank you, Kris."

Ralsei pulled himself away from Kris and rushed over to the other side of the encirclement. They were now standing directly on either side of Deltarune.

Deltarune climbed back onto their feet, trembling, their eyes filled with rage.

"Darkners!" Ralsei shouted. "Hold your formation!"

Ralsei raised his hand into the air.

Beams of white and purple light streamed around the entire triangular formation, creating visible contours where the line was solid. A curved triangle materialized around the entire formation.

Another three beams flew towards the "trident" formation at the bottom of the triangle, creating three smaller equilateral triangles: the upright ones on either side and the inverted triangle at the centre facing downwards.

One last beam shot towards Deltarune, creating a sphere of pure light around their body.

The symbol was forming.

"Now!" Ralsei shouted out. "The lullaby!"

Kris closed their eyes and sang the lyrics.

A strange light fills the room,

Twilight is shining through the barrier.

It seems our journey is finally over.

Despite everything,

It's still us,

Our hearts full of determination.

When Kris opened their eyes, two gleaming white wings had spread out from their back and from Ralsei's.

Delta Rune was complete.

The entire room grew silent. In that moment, something happened that none of them, not even Ralsei, could truly understand. It was the spell that would stop Deltarune from hurting any more people.

The 'space' around Deltarune suddenly caved in on itself, forming a vortex that began pulling everything in.

Deltarune's body contorted and sank into the vortex.

"Get out of the formation!" Ralsei shouted.

At once, every monster broke from the lines, dashing towards the edge to begin frantically climbing down from the rock. A few jumped off, having placed their bets on being revived after the healing Fountains returned.

Kris, Susie, and Ralsei were the only ones left within the Delta Rune formation as the vortex continued to expand.

"Susie!" Ralsei shouted, rushing towards her to heal her. "Are you okay?"

"Ugh...I'm going to feel this one in the morning," Susie said, clutching at her broken wrist. "Ralsei, what happened?"

"This is the spell that my ancestor, the original Deltarune, had cast to create the Dark and Light Worlds," Ralsei said. "All space inside the Delta Rune becomes sealed off from the external world. We...created a second Dark World, one where the human Deltarune will be trapped in for a very long time."

"What? There are two Deltarunes?" Susie shook her head, sighing. "Well, we better get out of here then! Wouldn't want to be trapped in there with them, would we?"

Something began shining out of the vortex. It looked like the glowing wall from the East Fountain that Susie and Kris had passed through to return to their world the first time they came here.

"That's the West Fountain," Ralsei whispered. "Having been forged from the original Deltarune's magic, they are the only substance capable of resisting the vortex. That's why the fountains are bridges between the Dark and Light Worlds."

"Will this Fountain take us back to our world?" Kris asked.

Ralsei nodded. "Yes. You should hurry, before the vortex expands past the Fountain. You won't be able to go back if that happens."

Susie didn't waste any time. She was already on her way there.

Kris paused, feeling something hot rising up into their face.

"Kris?" Ralsei spoke.

"Ummm...I..."

"Kris, what's wrong?"

Kris turned towards Ralsei as their vision grew misty. "I might not be able to come back for a long time. I...didn't exactly leave my world on the best terms. It'll be a while before my family and my friends can forgive me."

Ralsei lowered his head. Then, he took off his hat.

"I'll be waiting for you," Ralsei said, his cheeks going full blush. "I promise."

Kris couldn't stop the warm, salty tears from flowing down their cheeks. "Please don't wait for me, Ralsei! You're a great prince, with so many good friends. You don't have to worry about me."

Ralsei shook his head.

Then, he leaned forward and kissed Kris on the lips.

Kris's tears became accompanied by a blush as full and red as Ralsei's.

"I'll always wait for you," Ralsei whispered. "You've forever made a place in my heart."

"Ralsei..."

He took Kris's hand and pointed them towards the Fountain. "Go, Kris. There's no time left. This is your only chance to get back to your world."

Wiping away their tears, the feeling of Ralsei's lips still warm on theirs, Kris nodded and took a step towards the portal.

Their hand trembled as they let go of Ralsei's.

"Don't worry, Kris," Ralsei said behind them. "We'll definitely see each other again."

"I know," Kris replied. "I'm...I'm ready. I'm ready to face my world again."

"Good!"

Ralsei waved goodbye.

"Just one more thing," Kris said, turning around. It was so hard to pull their gaze away from Ralsei's beautiful eyes. "That song you taught me – I know it. I've heard the lyrics before. Does the song have a name?"

"I...don't know."

"Let's give it a name, then!" Kris gave a genuine smile. "When we're apart, we can sing the song to remind us of each other. It'll be our song. Our lullaby."

Kris stepped in front of the portal.

"I like it," Ralsei called out, the last time Kris would hear his voice in this world. "I like it, Kris! That's what I'll call it from now on. Our Lullaby."

Without turning around, still smiling, Kris raised their hand and waved goodbye as they stepped through the Fountain.

The world flashed before their eyes.

Kris knew that things wouldn't be easy ahead. It wouldn't be easy apologizing to everybody, to their friends, their teacher, their mother. But they held on to hope.

The hope that one day, they would see Ralsei again.

The hope that the next time they were together with Ralsei, it wouldn't just be the two of them in the Dark World. It would be underneath a warm noonday sun, or beneath an umbrella sheltering them from the wind and the rain, or under a night sky full of glittering stars and a glowing crescent moon.

The hope that, in the future, when the sun shone its light upon Kris, it would cast a silhouette of two shadows walking side by side, hand in hand.

Filled with this hope, Kris opened their eyes.

The future belonged to them together.

Thanks for reading this story!

I can't wait for Toby Fox to release the full Deltarune. I guess part of my motivation for writing this story is to try to fill in the plot of Deltarune to relieve my anticipation. But mostly I wrote it for the Kris/Ralsei fluff :)

If you liked this story, please leave me comments or suggestions to help me improve my writing!