The Beginning



Undertale starts off by telling us the story of the monsters war against the humans that ended in the monsters being trapped underground by the barrier. The barrier is a magical seal that can only be broken by 7 human souls or exited by a human and a monster soul fusion and it can be entered by anyone. Many years later after being trapped underground, Queen Toriel and King Asgore have a child named Asriel.

Asriel and Chara



This is where Chara (the first human, the one you named) comes in. After an unexplained amount of years, Chara falls into the underground. The injured Chara calls for help then Asriel saves them. Later in the game you will be treated to the story of Asriel and Chara. After the king and queen take in Chara they fall deathly ill and die. This causes Asriel to want to fullfill the humans last wish to see the flowers from their village. Asriel does this by absorbing Chara's soul and crossing the barrier. However, this kills Asriel in a tragic misunderstanding by the humans. At first, it seems like a tragic tale for the human but there is a dark twist. You will find yourself at the true lab where you learn by watching the tapes that Chara had a dark plot to kill themself, possess Asriel and use their immense power to destroy Humanity. Asriel says when you talk to him after walking to the very first room in the ending sequence that the control was split between them when he absorbed Chara's soul and Chara's soul wanted to kill the humans but he resisted (causing him to die of wounds). He also says Chara, for unknown reasons, hates humanity. The tapes in the true lab heavily imply that chara poisoned themself with buttercup flowers that they learned were poisoness after accidently using them in a pie for Asgore. Then they most likely used Asriel by playing to his nice side making a last wish that could only be accomplished by them merging souls. So in theory, Chara fell into the underground, got adopted by the royal family, found a poisoness flower and killed themself to merge with Asriel to kill all humans but failed when Asriel resisted causing them both to die. Asgore in a fit of rage over his children's deaths, orders all humans that fall into the underground must die and that with enough souls he will shatter the barrier and bring eternal peace by simply destroying all of the humans. Disgusted with his actions, Toriel leaves Asgore never to be seen again. Toriel sets up home at the entrance/exit to the ruins after leaving Asgore.

Alphys and "Determination"



Then Alphys comes in. Alphys meets a ghost (who apparently is the cousin of Napstablook, I keep hearing this but I have no evidence for it); this ghost wants to be a star and Alphys wanting to impress Asgore (who she has a crush on at this point in time) makes the ghost a robotic body. From this point on, the ghost is Mettaton. This is evidenced by the journal in Napstablook's neighbor's house which can be opened with the mystery key from Bratty and Catty. She presents Mettaton to Asgore. Impressed by the soul technology, he employs her as the royal scientist to find a more peacefull way of opening the barrier. Alphys' studies lead to the extraction of "Determination", a force humans have that allows their souls to persist after death. Alphys injects "Determination" into dying monsters trying to find a way to make their souls persist after death as a possibility to use them to break the barrier. This experiment goes horribly wrong and causes the monsters to melt and mold into terrible (friendly????) creatures as they cannot maintain the determination causing them to lose form. During these experiments she finds that a monster cannot absorb a monster soul and a human can't absorb a human soul so she must create a new living vessel to hold the souls of the "Determined" monsters. This whole plan fails but the vessel she made was made by injecting a flower with "Determination" creating, you guessed it, Flowey (this is all evidenced by the logs on the walls in the true lab and Alphys own dialouge in the true lab cutscene).

Flowey



The last thing before Frisk is the backstory of Flowey. In the genocide run while you're in Asgore's house, the story of Asriel and Chara is replaced by a speech by Flowey. Flowey tells you about how when he was created he couldn't feel emotion, not even for his parents no matter how hard he tried (by the way, if you aren't aware, which means you didnt beat the game yet Flowey is Asriel or at least pieces of him). Flowey then decided a world without love was not worth living in so he killed himself but his "Determination" brought him back at his "save" point, the garden he was created in. Flowey began to experiment with this discovery. He decided to help and spare at first but after he learned everything about everyone's life, it became boring. He then decided to do evil things out of curiosity, But is stopped by Sans multiple times. Flowey says that Sans caused him many resets and that he is a smiley trashbag. Creating the Flowey we meet at the start. (I just want to say Flowey in a way is a representation of the player. At least in my personal experience I did seven pacifist runs choosing every option, and just in general replaying the game but then the curiosity to see new things overcame me and I did a genocide run to see what happened).

Let me begin by stating that Undertale, if you didn't catch on, believes resets, saves, etc as canon, which also means every copy of Undertale ever played is set in its own slightly different universe. What I mean is that if you do true pacifist and only true pacifist, you have created the happy ending universe. If you do genocide,and never do anything else but genocide after or never sell your soul to Chara, you have the destroyed everything ending universe. If you sell your soul and redid the pacifist ending, releasing Chara onto the world, everyone dies but the world itself lives on. I call this the true genocide ending. Then there are slight differences in everyone's universe based on what you've done in the middle, like all your neutral endings. (but the neutral endings really dont matter at all.)


True Pacifist



This one is self explanatory. Asreil breaks the barrier after his fight and everyone lives happily ever after except Asriel, who sadly turns back into Flowey. To maintain this, never true reset or when you do never do a genocide run. Always leave the game off after a true pacifist run! (You can do a genocide run, just reset after killing Sans and watch the ending on youtube, because screw consequences and having to mess with files to fix it!)


Genocide



After killing everything in the underground, your determination is so great it resurrects Chara. Chara, after explaining their ressurection, ask you to delete this world. No matter what option you choose, it will lead to your death and the worlds destruction! Chara will offer you a world reset for your soul. For the genocide ending, don't sell your soul or sell it and only play genocide or neutral runs for the rest of your life.


True Genocide (Post-Genocide)



Accepting Chara's soul sell offer then doing true pacifist causes Chara to use you to do a true pacifist run so that the barrier will break. This will free Chara and as seen in the two post genocide endings, Chara takes full possesion of Frisk's body and stays with Toriel. However, if you choose the "Better places to go" option, a picture of all your friends and "Frisk" is shown with all of their faces scribbled off in red marker except Frisk. This very heavily implies Chara took you over and then killed everything, humans and monsters alike, basically commiting "True Genocide". (This can never be fixed. It is a permanent consequence and the only way to remove it is by messing with game files.)

The 6 Humans Before Frisk



The humans before you obviously died; but where, when, and why? Now Chara is not part of the six human souls, seeing Chara's coffin has a red soul when seen in the basement of the castle and Asgore is not in possession of a red soul meaning Chara's soul is somewhere else or was destroyed when Asriel died. The Flowey boss fight soul mini games each feature 1 of the 6 weapons found in game. The worn dagger and real knife do not count. The worn dagger is Asgore's gardening tool and the real knife is Chara's old knife. As i was saying, this suggests each weapon was used by the corresponding soul when they were alive. There is also a piece of armor for each weapon (toy knife with faded ribbon, tough glove with manly bandanna, ball shoes with old tutu, torn notebook with cloudy glasses, burnt pan with apron, empty gun with cowboy hat). These sets are found in relativly the same location near each other, suggesting these humans died where the weapons are found. For example, maybe someone was chasing a human who hid behind the waterfall and was found by that person, who then cut off the old tutu as seen in its sprite it seems torn. Then, the human hid in the patch of tall grass. We find the ball shoes in where they were killed as would have happened to us if we were standing a bit to the left in that 1 scene with monster kid. This is how i think they died, where the weapon is found after an encounter that cut their armor off. The vendors with armor weapon combos found them where the humans died, most likely the tutle guy (Gerson), since collects junk he finds and catty straight up says she found the gun in the dumpster. Now the killer is up for debate the main competitors for this spot are Undyne, since she has a custom of telling a tale to humans before killing them, suggests she has killed before. Then Sans who could be trying to stop the anomaly by killing humans. I will explain this in the next section.


Sans, the Guardian of the Timeline



Sans is very heavily evidenced to be a time traveller that with all the stuff I have found on him, it is pretty much canon. First off lets discuss the Sans room easter egg where to access his room, you have to save in the judgement hall and reload multiple times. Sans seems fully aware of your ability to save and reset here, asking you to give him a secret code and you reloading to give it to him. Sans' room is further evidence to this as there is the physics defying trash tornado, the lab with the blueprints, photo of you with people you dont know and the strange machine. It really is all very clear. Sans is also shown to have alot of interest in science fiction and owns a quantom physics joke book. Possibly, this is to show Sans is both a genius and a light hearted comedian. This is pretty much made fully canon when you fight Sans in genocide. He says something along the lines of "our reports showed a massive anomaly in the timespace continuum. Timelines jumping left, and right stopping and starting..." "until suddenly everything ends". So even if Sans can't travel through time, he can at least observe the timelines. Sans also shows the ability to teleport and one of the calls to Papyrus seems to hint at Sans teleportation ability when Papyrus says he seemed to just appear on the other side of spikes that Papyrus had to jump over. Sans in the Grillby's scene possibly shows the ability to stop time when the spotlight is on Frisk and Sans, everything else stops moving and becomes grey. Even the fire of Grillby's head stops. Sans is also extremly powerful seemingly more powerful than Asriel in his final form atleast his fight is much more difficult than any other fight in the game. Sans' powers may stem from knowledge. Observing the universe timelines may have taught him how to do these things or simply using the machine gave him the powers kind of like a super syrum that heros get their powers from. It is unclear at this point exactly how he became this powerful, these are just ideas. Just to answer this question Sans doesn't destroy Frisk the anomaly immediatly because of his promise to Toriel. Sans also doesnt kill you because in his genocide dialouge he mentions he thought he could stop you peacefully by being friends with you.


W.D. Gaster



By looking through all the stuff on Gaster, I think I may have a clear backstory for him now. Lets get what we know out of the way. Gaster doesn't enjoy being mentioned as using his name in name select causes him to send you back to the menu screen. Gaster is seen in a randomly appearing room. Gaster as evidenced by the grey NPC dialouges, was the old royal scientist before Alphys. Gaster also created the core and died in an accident presumably falling into it which caused him to split into many pieces. Finally W.D. Gaster may be Wing Ding Gaster or Wing Ding Aster. This is my theory from this and other surrounding information that may relate to Gaster. Wing Ding Aster, which i assume is his real name since it's a font and the fact that his face kinda resembles a cracked skull, leads me to believe he is related to Sans and Papyrus. Now we could assume he is just a skeleton and that all skeletons are named after fonts, but it would make a lot of sense for Gaster to be their father. The reason he is likely their father is that Gaster would have influenced his children to be scientists, which Sans pretty much is. Papyrus is not because y'know...he's dumb as rocks. This would also explain why Sans is the role of father to Papyrus after their dad died. Sans bought papyrus action figures dressed as santa, read papyrus bed time stories and in dialouge between Undyne and Papyrus, we find out he even pays the house bills. This would suggest that even if Gaster is not their father, Sans and Papyrus father died awhile ago as they are not seen grieving at any point in the game so it must not be recent. Now this is where it gets interesting, Sans said "our reports" from last section "our" must refer to a person he worked with which could really only be Alphys or Gaster. If Gaster was their father it would be almost guarenteed that Sans and him would work with each other. Gaster may have also died on purpose after finding out about the anomaly or maybe the core was originally built with the secret purpose to fuse Gaster into the worlds timeline. Gaster would do this to stop the anomaly by trying to control time and space, which kinda worked. He does seem to be able to change things in the universe at will, such as making things that mention him dissapear. So in short Gaster and his son found the anomaly, Gaster killed himself by falling into the core to merge with the timeline to stop the anomaly and Sans took a sentry job to watch for the anomaly who he finds out is Frisk while taking care of his little brother, Papyrus. Also if their is still secrets to be found, I believe we may be able to find all the pieces of Gaster and reassemble him since the pieces are definatly gatherable. This is shown because the grey NPC that talks about Gaster spliting apart is holding one. Could Gaster coming back be a plot for future DLC if there ever is any? Also, through editing the files of Undertale you can see a hidden "diary" entering from who we can assume is Gaster due to it originaly being in Wing Dings.

"ENTRY NUMBER SEVENTEEN: DARK DARKER YET DARKER THE DARKNESS KEEPS GROWING THE SHADOWS CUTTING DEEPER PHOTON READINGS NEGATIVE THIS NEXT EXPERIMENT SEEMS VERY VERY INTERESTING ... WHAT DO YOU TWO THINK?"

This passage was translated from the Microsoft Word font Wing Ding.

Chara. Human, Monster, or Something Else................




Chara is constantly refered to as human but are they human? There is the fact that they are always called human and they can't be a monster or else the other monsters would realize they are one. But in the ending of genocide I can't possibly pass that off as human. Their face contorts into demonic shapes, they can possess people like Asriel and Frisk unlike any other human soul I know of. There is also the fact that Chara merges with Frisk in the end of genocide but remember the true lab. Alphys' studies showed Humans can't take other human's souls. This seems to point to one thing. Chara is something else...........

Frisk Mystery



Frisk is a mystery that I can't solve. They are truly an anomaly in the timeline. Flowey in his genocide speech asks how you were resurrected, believing you to be Chara, and then says maybe Toriel took you to the ruins for a proper burial suggesting Frisk is a reanimated corpse. Then when talking to Asriel at the end of true pacifist he asks why you climbed the mountain and fell into the underground. Then there's people speculating Frisk is the good half of Chara and the two of them were the ones being talked to in Gasters number 17 entry written in Wing Ding's. This is fully up to the reader of this guide's interpretation.

Chara and Frisk Connection



As seen in the picture above, Chara says that their soul and determination are yours. This raises a question. Is Frisk just Chara reborn? This heavily suggests that. There is a lot of evidence to support this such as how you seem to have just appeared in the Underground. Remember Chara is the one who fell, not you. When you pick other places to go in the end of pacifist it seems Frisk has nowhere else to go. We never get to see their parents if they even has any, and if they did have parents, how would they be allowed to stay with Toriel? Then there's the fact that Flowey mentions in his genocide speech that Toriel likely buried Chara in the ruins when she left Asgore, are you a reanimated corpse? With this new evidence I have to believe that when Chara died their soul somehow was born into a new body. How or why is unclear and Frisk was born where we start the game they must have simply appeared there. This also has some major supporting evidence in how Sans says that you are an anomaly in his genocide fight. An anomaly is something that randomly appears in a timeline, something unexpected, so you must have just appeared, if you had previously existed you would just be part of the timeline not an anomaly.