Undertale: The Underground Beast

What if there was something Underground before the monsters were trapped there in the first place? What if there was a beast loose in the Underground? 
== Story ==
Once upon a time, long before the monsters have been imprisoned in the Underground, an ancient beast had lived there. When the monsters were imprisoned after the events of the war, the beast kept itself hidden as the monsters built their cities in its home.
But all that changed when Chara fell down, and the beast decided to rear its ugly head, and despite it following primal instinct, it is semi-sentient and it knew how powerful a human SOUL was, and that seven of them would make you a god. So, it intercepted them before Chara could make out their plan, killing Toriel in the process. Asgore put up a good fight, driving the beast back to its cave, but at the cost of his death, leaving his children behind.
The remaining Dreemurrs: Asriel, the crowned prince, and Chara, his adoptive human sibling, were very devastated at what had happened, both of which retreated into the Ruins for a while, leaving the Underground in a short period of anarchy, until they were found, both of which were in their teens. Asriel was soon taken to become the ruler of the Underground, while Chara remained in the Ruins to take care of it.
Asriel then passed a law that said that the SOULs of any dead human must be taken to him, for the purpose of preventing the Beast of the Underground to get its claws on them. The monsters misinterpreted it as killing humans, and despite Asriel's attempts, they still did it. Of course, Chara knew that Asriel did not want to kill innocent humans, but she was forced to stay in the Ruins.
Now, due to the anarchy, Gaster never had time to construct the CORE, and focused more of his attention on his two children to protect them from the beast. He eventually hired an assistant, Alphys, to help him with his work when Asriel was found and made King. During the period of anarchy, he found the bed of Echo Flowers in which the previous king had died in, and snuck in a pinch of DETERMINATION, and injected it into one of the flowers. He thought it was a failed experiment, and went off. But, he did not see the flower gaining the former king's mind and memories, becoming Echo the Echo Flower.
As for his two sons, Sans knew about what had happened with the beast, and had joined the Royal Guard to protect Papyrus from it. Meanwhile, Papyrus began working under his father's wing, going on his way to becoming a scientist. Since Waterfall was where the beast lurked and prowled, most of its residents fled to either side of the Underground out of fear, leaving only a few residents and a couple of survivalists to fend for themselves, and the only way they could get through the zone was through specific paths and/or armored trucks designed to withstand a beast attack.
Undyne casually patrols the area, searching for humans to capture. She was more than determined to gather all seven SOULs before the beast could, not knowing what horrid things would happen, nor did she want to know what happened. Gaster and Alphys, meanwhile, began working on all sorts of weapons for not just fighting against humans, but against the beast as well. Mettaton was an example, with his boxlike form being a compact state to store his NEO (Genocide Route) and EX (Neutral/Pacifist) forms. Without the CORE, he had more land to build his resort upon, even building a small power plant to power it.
One by one did six humans fall down, but whenever the beast struck, Undyne managed to drive it back to its cave before the human arrived. With more of those SOULs, Asriel became more and more nervous of what was happening. But, he had to stay strong. When the eighth human arrived, no one, not even the eight human themselves, would know what will happen next.
== Roles ==
(Original Role - Character)
The Protagonist - Frisk
The Fallen - Toriel
The Empty One - Echo / The Beast of the Underground
The Caretaker - Chara
The Recluse - Napstablook
The Judge - Papyrus
The Ambitious - Sans
The Captain of the Guard - Undyne
The Royal Scientist - Gaster / Alphys
The Celebrity - Mettaton
The Monarch - Asriel
Omega Flowey - The Beast of the Underground
The Soulless Angel - Echo / Asgore
== Characters ==
=== Undertale Characters ===
==== Frisk ====
Frisk is a kind, caring, and sweet orphan that fell down because they was being pushed by bullies down the mountain during a field trip. Despite their kindness, they are far from an innocent angel. They can be sassy from time to time, and have a knack for anything that lets them get creative.
==== Chara ====
Chara remains in the Ruins as its caretaker. She has remained trapped in there ever since a misinterpretation in the law. Over time, she has gained the ability to use fire magic, and lives in the house she and Asriel had tidied up and grew up in. Despite being cooped up in the Ruins, she manages to get outside information from friendly monsters, and is aware that there are six humans SOULs in store. She adopts Frisk to protect them from the Beast, and like Toriel, she has a knack for cooking and wears a black version of her robes.
Themes
* The First Human (Fallen Down)
* Childhood Tension (Necessary Tension)
* Devastation (Heartache)
==== Napstablook ====
Ever since the Beast incident, Napstablook became very scared of what happened, despite being a ghost that cannot be harmed. He is little different from his original counterpart, and the Snail Farm has been moved to another spot in Waterfall, further from the Beast's lair. He goes in the Ruins from time to time because of his friendship with Chara.
Themes
* Ghost Fight (Ghost Fight)
==== Papyrus ====
Papyrus, and his older brother, Sans, are the two sons of W.D. Gaster. He had been born during the anarchy period, so he never came to know of Toriel or of Asgore. With Sans in the Royal Guard to protect him, he went to follow the footsteps of his father, becoming Gaster's apprentice in science and cooking. He is still pretty goofy and eccentric, but he is much more aware with a beast on the loose.
Themes
* The Great Papyrus! (sans.)
* It's Really Quiet out There (It's Raining Somewhere)
* Spaghettilovania (Megalovania)
==== Sans ====
Ever since information about the Beast of the Underground has gone wild, Sans had began training and showing his power even more so he can protect his family, especially his little brother, Papyrus, ever since he was born. He still enjoys puns, eating hotdogs, and he is more active with the facts that Gaster taught him how to cope with his abilities there is a beast on the loose, and is still aware of the RESETs and of LOADs.
Themes
* Sans + Lazybones (Nyeh heh heh! + Bonetrousle)
==== Undyne ====
Undyne was a teenager when the Beast of the Underground attacked, and she had a spark within her that motivated her to train nonstop, and she quickly climbed to the top of the chain, achieving her canonical position as the Captain of the Royal Guard. She knows of the threat the beast is and fears it, and she cases humans around not just to take their SOUL, but to make sure that the Beast does not grow stronger. She is slightly harsher to the Guard, but for a very good reason. She can still become Undyne the Undying.
Themes
* Determined Justice (Spear of Justice)
* Battle Against a True Protector (Battle Against a True Hero)
==== Gaster ====
Due to the period of anarchy that beseeched the Underground, the CORE wasn't built, and Gaster was able to remain in the real world, and retained his position as the Royal Scientist. He taught Sans how to cope with the ability to remember RESETs, and taught Papyrus in the fields of science. He had hired Alphys as an assistant to help him with his work, and they created the Amalgamates for the purpose of making super-soldiers to hunt and kill the Beast of the Underground.
==== Alphys ====
Since Gaster never fell down, Alphys never became the Royal Scientist. Although, she became Gaster's assistant and helped him with his studies. She is still crazed with anime, but not as much since there was less to begin with since the anarchy period. She and Gaster created the Amalgamates as a failed experiment to produce an anti-Beast weapon.
==== Mettaton ====
Even before the Beast showed up, Mettaton always wanted to be a star, but his request got delayed by the period of anarchy that it had caused. Thus, he was granted a robot body made to fight the Beast. He used this body to become the Star of the Underground for the purpose of being a light in the dark. His box form was equipped for more compact travel, since his NEO form in this timeline is slightly bigger and more durable that the original in the canon Undertale, making it more of an actual boss fight.
Themes
* Beast Crusher (Metal Crusher)
* Death By Glamour (Death By Glamour)
* Power of NEO (Power of NEO)
==== Asriel ====
Asriel had taken his father's place as the King of the Underground ever since he was found, and he is very inexperienced with his rule. Despite this, he tries to keep his subjects happy, and is plagued with the guilt of seeing six innocent humans die, some even by his own hand. He is also devastated by the death of his mother and his father, and wishes he was strong enough to have taken down the beast. He wears his father's crown and cape and a more armored version of his mother's robe.
Themes
* Der verwaiste Prinz + Asriel Dreemurr (Bergentrukung + ASGORE)
==== Toriel ====
Toriel was the mother of Asriel and Chara before the Beast killed her. She speaks in purple text, and while she is not the narrator, she does give off her thoughts and feelings from time to time, especially those that revolve around her children.
Themes
* Heartbreak Strikes Back (Megalo Strikes Back)
==== Echo/Asgore ====
After the death of his wife, Asgore began to fight the Beast of the Underground, and the two were engaged in a fight as the King of the Underground pushed him back to Waterfall. He managed to save his children from the wretched creature, but at the cost of his life, and his dust scattered onto an Echo Flower. Gaster found the flower and injected it with DETERMINATION, causing it to gain sentience, with Asgore's consciousness and memories, but not his SOUL. On the True Pacifist Route, the Beast is dead, so he manages to intercept and absorb everyone's SOULs to revert back to his original form. After saving him, he says that he is proud of his children, battering through the odds, but he doesn't know what will happen to him.
Themes
* Your Old Buddy (Your Best Friend)
* Fallen King (Hopes and Dreams)
* Salvage the World (Save the World)
* Sein Thema (His Theme)
=== Added Characters ===
==== The Beast of the Underground ====
This vile creature has been trapped in the Underground long before the war, and mainly follows primal instinct, but it does know when it should strike. It ambushed the monsters after Chara fell down in order to absorb their SOUL, but failed due to Asgore protecting his family. It lives in a cave within Waterfall, where Undyne patrols regularly to make sure she gets another human before it does. It takes the place of Photoshop Flowey as the final boss of the Neutral Route.
Themes
* Incoherent Growling (You Idiot!)
* Feral Nightmare (Your Best Nightmare)
* A Beastly Climax (Finale)
== Locations ==
=== Undertale Locations ===
==== Ruins ====
The Ruins are slightly more worn down from the original because Chara was not as motivated due to her mother and father being killed by the Beast of the Underground, and some of the rooms were overrun with vines and moss. Toriel's house belongs to Chara, who spends most of her time there.
==== Snowdin ====
Snowdin is not that different at the beginning, but Snowdin Town is bigger because some of the families have moved there because of their fear of the Beast of the Underground. Due to this, Grillby had to grow his restaurant in order to accommodate for the new customers he had.
==== Waterfall ====
Most of the inhabitants moved out because of the Beast, with the Temmies, Napstablook and Undyne being the only ones who still lived there, save for some survivalists. Most of the buildings there are in ruins due to there being no caretaker for them. The Beast lives in a cave in Waterfall, and most monsters travel through the watery landscape via armored trucks. There are far more valuable items in Waterfall due to fewer monsters being daring enough to collect them.
==== Hotland ====
Hotland did not have as big as an increase in population as Snowdin, but there was a small number of inhabitants that are more tolerant to the heat located there. Gaster's Lab is set in Hotland, and the True Lab is still set under Gaster's Lab, but it is less run down than in the canon Undertale.
==== MTT Resort ====
Most of the former residents of Waterfall that went east had came through the MTT Resort, which had been upgraded to accommodate the refugees. It is much bigger, due to the CORE not existing. It is still powered by geothermal energy like how the CORE does it, but it doesn't use magic for it.
==== New Home ====
New Home was where the remaining refugees, including Gerson, moved to. It hasn't changed that much from its canonical counterpart, except that Asriel lives in the Castle instead of Asgore.
== Trivia ==
* This AU was inspired a bit by my own thoughts, but as I developed it, I had thought more and more about Undertale: Curropted Justice, and Slight Alteration. It is partially inspired by them.
* It may seem a bit like a switch-up, here and there, but it isn't exactly one. With a beast on the loose and the previous rulers dead, some characters have different occupations.
Category:AUs
Category:Concept Change
Category:Special Event
Category:Serious
Category:Noble Dark