Chapter 1

Hey there readers, Darkus_Cyril here with a new story, this one is an Undertale/Fairy Tail crossover. I got the idea when I watched a playthrough of Undertale and watched up to episode 160 of Fairy Tail. Now as the title says, this will mostly focus on Lucy since she's the one to get the new Gate Keys. The spirits will be Undertale characters, you'll see who they are in the story, but I'm sure you can guess who some of them are. Frisk and Chara are female for this story, just to clear that up and their appearances are similar to the animation on Youtube called [MMD Undertale] - Megalovania - (Full Animated Fight) by puccagarukiss.

"Talking"

"Chara talking"

'Thinking'

'Telepathy'

Spells and Incantations

"Celestial King Speaking"

'Celestial King Thinking'

Disclaimers: I do not own Undertale nor do I own Fairy Tail.

Sans stood in the Final Hall in front of the Thing pretending to be Frisk. The kind and innocent teenage girl was seemingly held hostage in her own body by the spirit of the hateful human who was raised by Asgore and Toriel many decades ago. Sans was exhausted, he had been at this for hours, maybe days, though for anyone not capable of seeing the timeline shifts, only a few minutes had passed. Sans was exhausted but he smirked as he tried keeping himself awake to prevent Chara from finding some way around his bone cage. The teen wore a blue shirt with two purple stripes on the torso and a single stripe on each arm. Her light brown hair fell just below her chin and the back of her neck. She wore black tights and blue shorts over them and had on black boots. Frisk's normally bright brown eyes had dimmed and were slowly turning crimson as Chara took hold over her body, the white dust coated knife held casually at her side, the dust from the monsters she had mercilessly slain as she made her way back to her former home in the underground.

Chara smirked as Sans' eyesockets slowly started closing. Whenever she tried to move to the end of the cage, Sans' left eyesocket would burst into a blue flame, with an iris matching the fire menacingly, and she would find herself pushed back to the center of the 'cage'. So Chara decided to bide her time, waiting for Sans' guard to slip. As she waited, she heard the soul of Frisk sobbing in the back of her mind. Chara didn't care, this world needed to end, she had suffered too much from others to trust anyone, not even monsters. She believed they would betray her sooner or later, just using kindness as a cover for their true intentions, just like 'they' did. Chara knew Frisk was bullied as well and so decided she was the perfect host for her, but she was surprised at how much Determination this girl had. How kind she was, how naive to the world she was, so weak, or so Chara believed.

Frisk had constantly interfered, helping Undyne by believing in the fish-woman like many monsters did, giving the monster some of her Determination to grant her incredible strength. Unfortunately for Frisk and Undyne, Chara also had access to Frisk's Determination and there for soon defeated her rather quickly, only Resetting two or three times. When Chara killed Papyrus, Frisk had broken down and gone silent, only rising in the fight against Undyne. Now Frisk was shouting, shouting at Sans to stay awake. Chara felt her try to slip Sans some of her Determination, but Chara had wizened up and blocked her every time the poor girl tried. Soon Sans fell asleep and Chara slowly made her way to the 'wall' of her 'cage'. Using the blade of her knife, knowing the 'toxic' nature of the bones she couldn't physically touch them herself, Chara softly moved the bones out of her way and made a hole. When she slipped out she smirked darkly and rushed forward, slashing at the sleeping form of Sans, all while hearing Frisk scream loudly for Sans to dodge.

It seems Sans heard her, because his eyesockets snapped open and he dodged and smirked,

"Didja really think I would-" Suddenly Chara turned and struck again, catching him this time.

|9999999|

Sans and Frisk both fell silent as Sans fell to one knee. Chara then noticed something different, Sans was bleeding. Never had she seen a monster bleed before, their bodies usually turned to dust right upon death. Sans must have been extremely powerful to survive a blow like that, if only just. Chara smirked before she looked surprised as Sans stood up, blood dripping from his mouth,

"Welp, I'm- *cough* I'm going to Grillby's." Sans then proceeded to stumble towards the opposite side of the hallway from Chara when she, and Frisk, heard him mutter as he left the hallway, his body slowly breaking away and turning into white dust,

"Pa-Papyrus, do you... want... anything?" Frisk was in shock as Chara turned away and moved on. She had the end this world, she felt a bit bad because she hurt Frisk, but she cleared those thoughts from her head. She, along with Frisk, would never suffer again, not from any one of those bastards! Chara soon made it to the palace and saw Asgore watering the golden flowers of his throne room. Asgore turned and saw Chara and had a thoughtful expression on his face, when suddenly the thoughtful expression turned to pained horror as Chara struck him down before he had a chance to speak. Chara had a wicked smile on her face as she watched Asgore die. Meanwhile Flowey popped up behind Asgore, still shaken from before,

"C-C-Chara, you beat him before I-I could help you? I-I'm s-sorry I was late... Wait... what're you doing? W-wait! PLEASE, PLEASE DON'T KILL ME!" Chara struck Flowey, the struck again, and again, and again until Flowey died. Soon Flowey's body shifted as Asriel's soul revived the body and reverted to his original form. Chara regarded the goat-like child passively as he looked up in fear and smirked darkly, before stabbing him, and watching him fade away into dust, as Chara's form shifted to her true form, with darker brown hair, slightly shorter than Frisk's, paler skin, and two rose cheeks. But the biggest difference were her eyes and mouth. Her eyes were pure black with crimson red irises, and her mouth dripped a pitch black liquid as she smirked darkly,

"Now, it is time for this world, and all who reside in it, to END!" Suddenly everything began to fade into blackness, the sounds fading and drowned out by Chara's insane and dark laughter, and soon only the ground Chara stood upon remained. Chara smirked before she froze with a look of shock, her body flickering between her form and Frisk's,

"W-what?! Frisk! What're you doing!" "NO MORE Chara, I will save EVERYONE from your madness!" Suddenly souls began appearing around Chara/Frisk. The Souls began to form the bodies of Papayrus, Toriel, Asgore, Asriel, Undyne, Mettaton, and finally Sans. Chara was shocked, how did Frisk pull them back from death? Their souls were nothing but dust on her hands and her knife, it should've been impossible! Chara shouted in agony as Frisk began forcing her way back into control. Pushing Chara firmly, but not harshly, for despite everything Frisk was not willing to hurt another soul, not even one such as Chara, into the recesses of her mind and her body returned to it's original form. Frisk felt her body stiffen as she used up all of her and Chara's Determination in the ressurection of her closest friends, except for Alphys, unfortunately Frisk did not have enough Determination to save her. Sans woke up first and looked around shocked before seeing Frisk lying on the ground. He knew it was Frisk because of the gentle look in her eyes, rather than the cold, distant look of Chara.

"Frisk!" Sans stood up slowly and made his way to the exhausted girl,

"Frisk, are you ok? Come on girl, don't fade away on me." Frisk smiled at him as she panted in exhaustion,

"S-Sorry Sans, I... I can't move right now, I used all of my Determination and all of Chara's Determination to save you all. I need to rest." Sans looked back and was shocked to see the group slowly waking up. Everyone looked around, minus Mettaton, who reverted to his original metal box form. Asgore looked at Frisk and then at Sans,

"Sans? Is that you? What has happened?" Sans looked back at Asgore,

"Frisk just saved everyone from Chara." Asgore and Toriel blinked as Asriel stood up shakily,

"Chara? But Chara died many years ago." Sans shook his head at Toriel,

"Chara did die, physically, but don't forget a human soul can remain even after the body has died. Chara took over Frisk after resetting the timeline over and over again. Frisk was being held captive in her own body by Chara." Asgore and Toriel were in shock, their adopted daughter did all of that? She was responsible for killing them? Toriel was crestfallen and she kneeled down and clasped her hands together in sadness.

"I-It isn't Chara's fault, not e-entirely." Everyone turns to Frisk,

"U-up on the surface, Chara was bullied and a-abused by everyone. Her birth parents were missing, they probably abandoned her or died from something, no one reallu knew. So she was adopted by a cruel family, and well, she was beaten and bullied until she grew to hate everything. W-when Chara thought I was too upset to do anything, I looked into her mind and saw her memories, trying to find out why she- she is the way she is. She was so angry at the world because of how she was treated. I was bullied a bit as well, but not too badly, unlike Chara. Chara was alone so she grew to distrust anyone. She even believed you all would betray her sooner or later." Asgore and Toriel were shocked. Sans frowned, as he heard of the reason behind Chara's hatred, there always was a hint of curiosity in the back of his mind concerning that. After all, no one was that hateful of the world for no reason, especially not a child. Sans frown turned a bit sorrowful as he knew the feeling of not having your parents around, his father W. D. Gaster having vanished several years ago, so he felt a bit of sympathy, and understanding, for the human. Toriel stood up and moved closer,

"I would never have harmed her. She might have been a human, but I saw Chara as my own daughter. I loved her just as much as I loved Asriel." Asgore bowed his head,

"I loved Chara just as much. I still wish she hadn't died so we could have proven this to her." Toriel glanced at Asgore with narrowed eyes before turning away as Sans placed hs hand on her shoulder,

"I recognise your voice. You're the lady from the door." Toriel looked up at Sans and smiled, (A/N: Remember that Sans never does see Toriel physically in the game, as far as I'm aware that is, if I'm wrong correct me, but that's the way it is for this story.)

"I'm glad you remembered, I do so hope we can share some more jokes with each other soon." Sans smiled and chuckled,

"Of course, who am I to deny a lady a couple of bad jokes." Toriel laughed softly as the two looked down at Frisk who was smiling at the two of them. Asgore looked on as Toriel, Sans, and Frisk interacted with each other and he looked down solemnly while Undyne patted his shoulder,

"It'll be alright, you old softy." Asgore looked up at Undyne and smiled softly,

"Thank you, and one day I will prove to Toriel that I regret everything I did these past few decades. Maybe then, she will forgive me." Undyne nods and looks at Frisk,

"She's so different from when I saw her earlier today. So much more like you, Asgore. Hard to believe she was being possessed, but seeing that light in her eyes, so much like Papyrus', that I can see she's pure innocence." Asgore nodded as Mettaton rolled over,

"Excuse me, Undyne. Do you know where Dr. Alphys is?" Undyne looked at the box shaped robot and sighed,

"Frisk said she couldn't save Alphys, she used all of her Determination, whatever that is, to bring us back from the dead." Mettaton turned to Frisk and tilted slightly,

"Determination is an unknown substance that humans possess. It is what allows their souls to remain even after their bodies have been destroyed. Dr. Alphys has extracted and tested this substance from the six previous humans who fell down into the Underground. Though, four of these humans died of natural causes and two died by by Asgore's hand, they were not killed by other monsters. And Alphys captured the souls and extracted Determination from them. Her experiments were... unpleasant for her, to say the least." Undyne nodded and continued looking at Frisk. Asgore stood up and looked around as Papyrus rushed up,

"Your Majesty! It is an honor to see you! Erm, d-do you know where we are?" Asgore turned and saw Papyrus and smiled slightly,

"Greeting skeleton, are you the Papyrus that Undyne has been teaching?"

"Yes, sir! She has been teaching me cooking! She says I've made lots of progress with my Spaghetti." Asgore smiled a bit more,

"That sounds marvelous, I would like to try some in the future, if you do not mind." Papayrus went on to make a speech about how he would be honored to cook for the king. Asgore smiled patiently as Papyrus rattled on and he started chuckling,

"It is good to see monsters with such kindness and the desire to do their absolute best. I will wait for your training with Undyne to finish, then you can treat me to your best plate of spaghetti." Papyrus saluted with an incredibly bright smile,

"Of course sir, I will study even harder and train even longer until I master the art of cooking!" Asgore smiled and nodded,

"Do you best, young skeleton." Papyrus turned to see Frisk and gasped,

"The human!" Papyrus ran over and kneeled beside Sans and Toriel,

"Human, are you well? I do hope you've become the truly good person I believed you could be!" Frisk looked at Papyrus and smiled softly,

"Thank you Papyrus, but I'm sorry for what Chara did to you. I tried stopping her, but she was too powerful." Papyrus looked confused,

"Who is Chara? And what are you talking about?" Sans tapped his brother's shoulder and explained the situation. When Sans finished, Papyrus was nearly in tears and he hugged Frisk tightly,

"To go through such hardships and still remain as pure as you are, you are indeed worthy of my friendship." Papyrus let go and posed his usual pose, making Frisk giggle a bit,

"So I, the Great Papyrus, will be your friend." Frisk nodded,

"Thank you Papyrus." Sans chuckled and shook his head before looking at Frisk, who started coughing slightly making Sans kneel beside her,

"So what happens now?" Frisk shrugged slightly,

"I don't know. Chara erased the world from existance, and I don't have the Determination needed to bring it back, not without sacrificing my own soul as a result. But if there is no other way, that is what I'll do, just so you all can return home." Everyone rushed Frisk and hugged her, shocking her as they held the group hug. Frisk smiled softly and hugged back. Toriel leaned back and smiled gently,

"Child, we would never ask you to die for our sakes. It would be selfish of us." Sans spoke up next,

"Yea, the world wouldn't be the same without ya, kid."

"Yes! I, the Great Papyrus, am telling you to live, so we may continue to be, friends." Asgore kneeled,

"Do not believe your sacrifice would go unnoticed, we all would feel lonely and afraid without your kind nature in the world." Undyne flicked Frisk's forehead,

"Don't wimp out on us kid. Live, not just for yourself, but for us as well!"

"I must admit, I am looking forward to whatever happens next. Human, I would want you to stay alive so you may see my rise to fame." Frisk smiled at the machine, and looked around at everyone and nodded.

"Perhaps I can help with this situation." Everyone looked up as a giant of a man wearing armor and an enormous white mustache appeared. Frisk however heard a sound and turned. She blinked as she saw Azriel hiding in the back of the crowd, not interacting with anyone. She turned to see Toriel and Asgore looking at the giant of a man before she stood up shakily, with Sans helping a bit. Sans was about to speak when Frisk shook her head and nodded towards Azriel. Sans saw him and blinked before looking back at Frisk and nodded. The two made their way to Azriel, who notcied them and seemed to shrink in on himself, as if afraid. To his surprise, Frisk simply hugged the goat boy. Azriel was wide-eyed and Sans smiled softly. Azriel smiled and hugged Frisk back. Sans turned and walked over to Toriel and gently elbowed her arm and nodded back towards Frisk and Azriel. Toriel looked and went wide-eyed as she silently gasped.

Toriel turned around fully and slowly walked back, everyone noticing and watching. Toriel walked up and reached out to Azriel, who was now helping hold up Frisk, before she stopped,

"A-Azriel?" Azriel smiled softly and nodded,

"H-hey mom. I've missed you." Suddenly Azriel and Frisk were pulled into a hug by Toriel. Sans looked back at the giant, only to see a kind smile on his face. Sans turned fully and faced the giant,

"So who are you?"

"I am the Celestial King, ruler of the Celestial Spirit world. As the ruler of that realm, I am capable of sensing other dimensions. When I sensed this dimension fading, I began to investigate. Upon discovering you all, the only survivors, I chose to give you the choice to come to my realm and become celestial spirits. As a celestial spirit you will have a key that you can give to certain mages in the realm of Earthland, to summon you." Sans thought for a moment before his pupils vanished, leaving the black pits of his eyesockets only visible, ready to fight if need be,

"And if we say no?"

"Then I will give you a set of choices for realms that you can go to, it is your choice." Sans thought again and looked at Asgore,

"Welp, you're the king, so it's your choice in the end big guy, I just want to stay with, and protect, Frisk and Paps." Asgore thought for a moment an looked at everyone,

"What do you all wish?"

"So long as I can be with my child and Frisk, I do not care, but this new world does sound intriguing." Toriel.

"I-I just want to hang out with Frisk and mom, and you too dad." Azriel.

"I wish to be with my cool brother! As well as my friends, Undyne and Frisk!" Papyrus.

"You already know my choice Asgore, you better bring Paps along wherever you decide to go, because he'll follow you and Undyne to the ends of the world." Sans.

"I wish to go, I will make my rise to stardom in this Celestial Spirit world and then in Earthland." Mettaton.

"As captain of the Royal Guard, it is my duty to protect and serve you my king. I will follow you anywhere." Undyne. Everyone turned to Frisk who blinked and seemed to grow shy,

"U-um, I feel like the Celestial Spirit world would be a nice place. If the ruler of that world is this kind, maybe his world would be just as kind.

With that, Asgore turned to the Celestial King,

"We will go with you. Just please make the summoner we are bonded to a kind person." The Celestial King simply smiled brightly,

"I believe I know the perfect candidate for your request. She is a young wizard, who is a member of a bright, and kind guild. Her name is..."

Earthland, Fiore, Fairy Tail Guild Hall...

"Lucy!" A blonde girl with her hair in a side ponytail looked up as her name was called and she smiled and waved,

"Hey Natsu, what's up?"

There's chapter 1. I hope I did alright with this little prolouge, I based a bit of the beginning off of the start of the fan comic, Aftertale, but only a little bit, and I mixed my idea, with that, and with the animation I mentioned up at the top. Now I need to figure out when and how Lucy will get the celestial spirits of the Undertale survivors. That will be decided in the poll I have set up on my profile so you can go ahead and check it out. Also, I wouldn't mind some ideas on what kind of keys these characters will have as Celestial Spirits, they won't be silver keys, and of course they won't be gold, the keys are in the thumbnail for this story actually, so I need to figure out a name for these keys, Colored Keys seems a bit too straight forward, but if I don't have any ideas, I'll just go with that.

Another thing, what I did with Chara's backstory, that's my theory as to why Chara is so hateful of the world, and wants it destroyed, after all, no one is that full of hatred for no reason, especially not a child.

I'll update this after I update some of my other stories. And don't worry, I will continue Dragonborn of Konoha and Orange Spark and Black Wings of Konoha since my flashdrive went missing, I'm starting from scratch with the latest chapters I had planned, so please be patient with me.

Anyways, I hope you enjoyed this chapter and hopefully I'll see you all in the next chapter,

Darkus_Cyril