* kid, listen. there are spoilers on this page; be careful when you're reading.
* you don't want a bad time, do ya?
"U SeE... dOwN HeRe, It's kIlL Or bE KiLlEd. TeM ReAlLy wIsH It wAsN'T, bUt iT Iz. BuT TeM DoNt wAnNa hUrT AnYoNe, So tEm'lL HeLp u iNsTeAd! U HaVeN'T KiLlEd mEh yEt, AfTeR AlL!"
Long ago, men and beast roamed the land. They lived in peace, but tensions slowly began rising...
... until one day, war broke out. Souls shattered, blood spilled, dust spread...
... and in the end, the humans won. Seven of their greatest wizards sealed monsters underground, deep, deep under Mt. Ebbot.
Travelers who climb the mountain never return...
But this is the tale of one who did.
The tale of one who saved monsterkind.
The tale of a fallen angel.
Note: this only goes over the main cast and a few other important characters.
Chara is a peaceful child, around the same age Frisk was when they died. Much like Frisk, their soul is blood red in color, and its trait is known as determination. They are the eighth fallen human.
Unlike in the common designs for Swapfell, they wear a shirt much like Frisk's own, except with a light stripe instead of a dark one.
Unlike in the original Underswap, Tem is peaceful and caring. However, unlike Flowey in Underfell, they're naive and cowardly. Strangely, like with Flowey in Underfell, they care for Frisk despite not having a soul. In this version of Swapfell, soulless monsters can, due to a strange quirk, still feel.
They used to be Monster Kid, Frisk's adopted sibling. However, unlike Flowey in Underfell, Chara never refers to them by their original name, because it's "too long. Tem's easier to say. Even MK's two syllables".
Asgore is, more or less, normal Underswap Asgore. He's a bit more aggressive, but he's not evil, moreso neutral. He doesn't believe in the "kill or be kill" mindset that monsters adopted after Monster Kid and Chara's deaths. After this mindset was adopted, his fur turned black in color and he left for the Ruins, bringing the Temmie doll that Monster Kid had cherished (which had recently been combined with determination by Undyne) and Frisk's body with him, burying the first human and keeping the Temmie doll in his home.
Hapstablook, sometimes known as Metta, is a reclusive ghost living in the Ruins. After his cousin Napstablook left to become a superstar, he shut himself out. He was close to Napstablook before he left, super close. Before the "kill or be killed" mindset was adopted, they both decided that they would play a show for any humans who fell after Frisk. But with that mindset, Metta decided to give any humans who fell after Frisk a show worth remembering.
After surviving his battle, Metta is surprised at Chara's willpower, and decides to let them pass, but to beware, as not all monsters will be as nonchalant as him.
Papyrus is, to say the least, an edge maestro. Some think that he cares for no one but himself, but he does care for his brother Sans, and eventually, for Chara and Tem. Though his attacks in and of themselves are weak, Karmic Retribution leads to damage being dealt throughout the whole fight - or it would, if Chara had bad karma, but instead, it heals them throughout the fight.
Sans is less of an edge maestro, but is still edgy to say the least. He goes all out in his fight against Chara, but thanks to Tem's healing Tem Flakes, and lots of determination and Bisicles, they survive the fight. Sans is impressed by the human's willpower, and lets them pass, telling them to beware as Alphys is quite powerful... and angry.
Asriel is an idolizer of the Royal Guard's captain Alphys. He is much more like his Underswap version then most of the characters, still being kind at heart, though he can be rude, stealing Chara's umbrella and insisting on holding it in Waterfall. Before Monster Kid and Frisk's deaths, he was jealous of them, due to his parents paying more attention to them then to him. However, after their deaths, he became quiet and rarely talked. While not showing it, he cares about Chara, showing worry when Alphys almost hurts them. Tem describes him as "a bit of a brat, but he has a big-heart once you get to know him".
After Alphys knocks Chara into comatose, he grows to despise her.
Alphys is the Captain of the Royal Guard. She is much more aggressive then classic Alphys, being ruthless and brutal. She almost kills Chara, but instead knocks them into comatose and takes them to Undyne's lab.
The royal scientist, Undyne is sadistic, to say the least. When Alphys brings Chara to her lab, she performs experiments on them, but due to Chara's determination, they wake up and fight back (as in spam the act options and spare command). Eventually Undyne allows them to get away, due to the fact that Napstaton will end up killing them anyways.
Originally named Napstablook, Napstaton is a robot and a celebrity in the underground. However, he doesn't want to be a celebrity, instead wanting to go back to the life he had before being forced into the robot body Undyne made. He convinces Chara to destroy his body, which doesn't add to the murder level due to Napstablook being fine. He then leaves to go to his house in Waterfall.
The queen of the underground, out of fear and grief after her adopted childrens' deaths, she put forward the mindset of kill or be killed, causing her people to grow cruel. She rarely exits her castle, and is a bit reluctant to fight you. In a True Pacifist ending, when you spare her, she doesn't trust Chara, and tries to kill them - this doesn't succeed, as Tem absorbs her, the human, and every other monsters', souls.
The former princette of the underground and adopted child of Toriel and Asgore, Monster Kid was at first jealous and a bit rude towards Frisk. Eventually, they grew to care for them after the human gave them a Temmie doll for their birthday.
They, in their God of Uber Life form, are the final boss of the Genocide Route.
The first fallen human, Frisk is kind-hearted, but more aggressive then Chara, who their soul is tied to. They are but a ghost now, only visible to Chara. They are the narrator.
At the end of a True Pacifist route, they thank Chara for their mercy towards all monsters, and tell them that if they wish to reset, to erase everyone's memories, granting them the True Reset option.
Note: this information is from the Underfell Wiki, and may be inaccurate to that AU and to Swapfell.
One of the two endings shown in the fanfic, Papyrus is the final boss in this ending.
Chara passes through the Judgement Hall unharmed, to their surprise, and defeats Toriel. Before she can attempt to kill Chara out of distrust, Papyrus kills her with a Gaster Blaster. While initially grateful (sort of), Tem and Chara are soon frightened as Papyrus absorbs her soul, and the human souls.
The fight pretty much plays out like the Omega Flowey fight, but instead of ending with the souls rebelling, Tem absorbs the souls that Papyrus holds, temporarily accessing their Monster Kid form before giving the monster soul to Chara, and they pass the barrier, living in peace for around a week before Tem realizes that a happy ending is out there.
True Pacifist Ending
Reloading their last save (just before the fight with Toriel), Chara goes through the Toriel fight. This time, Papyrus doesn't interrupt due to knowing how that will end. When Toriel goes to kill Chara and Tem realizes this, they absorb every monster's soul, and the human souls.
Monster Kid tries to break the barrier, but it backfires.
While at first the human souls were neutral, after being in Toriel's prescene for so long, they began to corrupt due to her negative energy, and they take control of Monster Kid, leading to the fight being against the human souls. After a soul is restored to their passive state, Monster Kid (in his God of Uber Life Form) restores Chara's health and they fight a Lost Soul (or two in some cases).
After Chara saves all of the Lost Souls and restoring the souls to their passive states, Monster Kid goes back to their normal form and breaks the barrier.
Not long after Frisk and Chara are prepared to leave for the surface, Monster Kid reverts to their Temmie form, and they take them with them to the surface, where they decide to live with Asgore, and everything is happy.
While not canon, this is shown in a what if chapter.
This chapter starts with Chara making their way through the Judgement Hall. The Papyrus fight is skipped, presumably being similar to the fight in the original Underswap and Sans' fight in the original Undertale.
Tem realizes that Chara wasn't acting out of fear, but rather, out of a bloodlust. They run off to tell Toriel to absorb the human souls, revealing their former identity, but before she can, Chara arrives and kills them. With her last breath, she tells Tem to absorb the souls and her soul, and they oblige, becoming Alpha Tem.
After Chara defeats them, out of sheer determination equaling the power of an eighth human soul, they turn into the God of Uber Life, and last a while before being beaten by Chara.
Frisk tries to stop Chara, manifesting an at least somewhat physical form, but is beaten and completely disappears.
At the end of the chapter, this is revealed to be a bad dream that Chara had. Tem comforts them, and they eventually go back to sleep.
- Swapfell has recently become the creator's favorite AU - however, the original publication of the fanfic was on June 13, 2017. It's currently hidden and a rewritten version of the first chapter is currently being worked on.
- Tem's friendliness is due to both Underfell Flowey and the creator's personal Underswap headcanon where Tem takes on a friendly role, helping Chara through the underground, though still soulless and with malicious intent.
- None of the sprites are made by the creator due to her lack of artistic ability.