Underswap

* Original
* Destroyed

The **Underswap** universe refers to the alternate universe originally created by P0pcornPr1nce, and is now under the ownership of the Undertale fandom similar to Underfell. The universe's characters are different, in that characters that had roles in the original universe being interchanged with each other.

In *Underverse*, Cross is sent here by request to Nightmare!Sans according to their own deal on torturing others for Nightmare's benefits. However, Cross is defeated by Underfell!Sans and Classic!Sans, thanks to some advice he got. This did not stop the arrival of a malevolent being, who is brought back thanks to Underswap!Chara, and he would begin to ravage upon what was Underswap.

## History

Underswap was one of the AUs Ink!Sans showcased to XGaster, whom he agreed to view them. Examining the universe carefully two timelines later, XGaster decided to attempt to replicate what has happened in Underswap in his own universe, but upon implementation he finds how imperfect the universe could be. He ends up overwriting this short timeline but not before his child calls him an "insecure old man".

Later on, after XTale is corrupted, Cross would be transported into this world by Nightmare. His first arrival got Cross confused, as he would soon realized that the AUs characters remind him of his own "friends". He saw this with Papyrus resembling that of his own brother, and without hesitation and having enough of these vivid memories, Cross tears a scar on Toriel and continues working for Nightmare.

Meanwhile, Sans is busy unpacking stuff that he carried from the underground with Chara. The two would be interrupted when Classic!Sans, Ink, and Underfell!Sans all emerge in front of them, and Ink is forced to hide the fact that they're actually alternate universes of him by claiming that they're clone about to die soon. Believing this, Underswap!Sans leads them all to the city to find Cross; when they do, he's worried on what Cross's true intentions really are. He tries to greet him as a friend, but when he tries to attack him, Classic!Sans and Underfell!Sans surprises him, and Sans takes back his other half. As all try to leave, Cross!Chara latches on to Underswap!Chara, taking 95% of their soul instead.

With this new provisioned soul, X-Event!Chara greet everyone and reprimanded Cross's own ideals. He feel compelled to tell Ink!Sans that he only wanted to see the full X-Event, but when the cast begins questioning this, XChara throws Classic!Sans and Underfell!Sans as well as every Underswap character minus Papyrus, Sans, and Chara to XTale, and has Nightmare lock Ink up. To demonstrate his true power, he overwrites Papyrus and Sans to live their worst memories, getting the attention of Nightmare.

Whilst still messing with Papyrus and Sans, XChara demands Ink to give him the other half of the overwrite button; his refusal causes a brawl between him and XChara before Ink manages to free Sans and Papyrus, the former fighting XChara for a while, until Papyrus tries to stop him because of the implications that he's hurting Chara in the process. When XChara forces Sans to use his blaster to kill him by overwriting him, Papyrus goes to block the attack, only to be harassed by Nightmare and forced to the breaking point.

Depressed and willing to let all the good memories go, he's willing to get killed by XChara, but Papyrus' unintentional good memories allowed Dream!Sans to take Classic!Sans and Underfell!Sans back to Underswap, and Classic!Sans' relapse of his Genocide timeline causes him to save Papyrus. XChara and Nightmare are brought to the knee as Sans, Papyrus, Classic!Sans, Underfell!Sans, and Dream uses the best of their abilities to defeat them. Not wanting to admit defeat, XChara tries to convince Sans by his concerns of his broken timeline that he could fix this, that he could create one universe with the best of others. Angered by XChara's unwillingness to fight, Nightmare stabs Swap!Chara, and him and XChara escape.

Now with Chara dying, their universe is at risk of being destroyed. Sans tries to convince Papyrus to join them to the next safest universe, Outertale, but depressed by having to live thanks to XChara's overwrite and untrustworthy of Ink, he refuses to go, opting to remain with a dying Swap!Chara. With Classic!Sans, Underfell!Sans, Swap!Sans, and Ink escaping to Outertale, and Dream going to XTale, Core!Frisk arrives and questions on why he did not come with the rest of the cast. After explaining that he could not live in a broken universe and that the rules have changed, Papyrus and Chara dies. XAlphys, who had just arrived thanks to the actions caused by XChara, tells her superior that there's nothing left of this timeline. As she was told what to do from XGaster, XAlphys throws the entire Underswap universe under quarantine, causing nearly all of XChara's soul to dissipate and all of the Underswap characters in XTale to disappear.

Because of this quarantine, it is one of two universes that survives the destruction of the Doodle Sphere from Error!Sans.

## Characteristics

Underswap is nearly identical to that of Undertale, but much of the original characters have changed roles significantly. For example, Toriel is swapped with Asgore to instead be the one to declare war on humans, Sans is swapped with Papyrus to be a naive person and is overoptimistic to join the Royal Guard, and so on and so forth.

After XChara's invention, much of the universe had been emptied out, moved directly to the XTale universe. Only a few rock formations remain to which both XChara, Swap!Sans, and the others fight. XAlphys later throws the remaining Underswap universe under quarantine, wiping it entirely empty.

## Characters

### Underswap!Sans

*See Underswap!Sans*

The naive Royal Guard that takes the original Papyrus' place, he was an optimistic person until the arrival of XChara. He tries to keep himself together even after his universe and his brother was taken down until he met his demise by XGaster.

### Underswap!Papyrus

*See Underswap!Papyrus*

The lazy brother that takes the place of Sans, he loses his faith in everything as XChara begins forcing him to live his worst memories, having to see his brother and the human die in his hands.

### Underswap!Chara

*See Underswap!Chara*

The human that ends up taking the place of Frisk, they became a damsel in distress as 95% of his soul is taken by XChara to use his own powers.

## Trivia

* super youmna and Jakei both make cameos during the introductory scene of Underswap in Underverse 0.3 Part 1.