Yo, don’t kill, and don’t be killed, okay?
That’s the best you can strive for.
— Monster Kid, in the epilogue
Monster Kid is the adopted child of Asgore and Toriel, as well as the adoptive sibling of The First Human and the true identity of Temmie. They are the final boss of the True Pacifist Route. Monster Kid has their personality swapped with Asriel.



Monster Kid is a yellow, reptilian monster with two spikes on their head, and a long tail. They have markings under their eyes, one appearing to be bigger than the other one, as well as protruding teeth. They wear a blue and pink striped shirt, which is similar to the first human's shirt, and appear to have absolutely no arms at all.

God of Hyperdeath

During this phase of battle, Monster Kid goes through some changes. They wear a long, dark robe that is similar to Asgore's with the Delta Rune on the front on their chest with a large collar and shoulder pads, along with a necklace that is similar to the heart locket. Their scleras become black, and their teeth become longer and sharper. They also have two black marks on each side of their face, right underneath their eyes, as well as arms that appear to be holographic. They also have three spikes instead of two, as well as having larger spikes.

During their battle with the protagonist in the True Pacifist Route, they have a multicolored rainbow-like background and they seem to be levitating across the screen.

Final Form

Although there isn't much info on Monster Kids Final Form, their it may look similar to Asriel in the original Undertale.

They are usually depicted as having a more sharp, geometric body, as well as longer spikes as well as sharper teeth. They might also have a pair of color chainging rainbow wings. Their body resembles the Delta Rune and the Angel of Death.

Main Story

Before the events of Underswap, Monster Kid found the fallen human, who was the first human to fall into the Underground. They became their adopted sibling and best friend. Just before the human died, they wished to see the golden flowers of their village, on the surface. Monster Kid absorbed their SOUL and the human carried their own body across the barrier to their home village. Monster Kid and their sibling shared control over Monster Kids body after their SOULS had combined.

The villagers assumed that the Monster Kid/Human fusion had attacked and killed the human child. The Monster Kid/Human fusion did not fight back but only fled. Lethally wounded, the Monster Kid/Human returned to the Underground and died. Once deceased, Monster Kid's body turned to dust, which spread across the garden.


Monster Kid, in their doll form, Temmie

Later, just before the king left, Undyne injected determination into a cat-dog hybrid doll that Monster Kid had previously owned. Initial experiments on the toy proved unsuccessful, and Undyne returned it to Toriel. Once Undyne left the doll, Temmie awoke.

Though Monster Kid's essence from the garden bed granted Temmie Monster Kid memories, she soon found that neither her mother nor her father could elicit any emotional response from her. She did not have a SOUL and thus, could not feel love, joy, or compassion.

Neutral Route

Monster Kid does not make an appearance during a Neutral Route.

However, when the protagonist falls into the Garbage Dump?, the protagonist hears MK's sound bite during a memory from MK's human sibling."It sounds like it came from over here... Oh! You've fallen down, haven't you... Are you okay? Here, get up... ... <Name>, huh? That's a nice name. My n a m e i s... - MK, upon finding the human Monsters also tell the story of MK and the first human during the walk in New Home.

The Story of Monster Kid and The First Human

This is the story told by monsters at the end of a Neutral Route. The song "Underswap plays during this sequence.

  • A long time ago, a human fell into the RUINS.
  • Injured by its fall, the human called out for help.
  • MONSTER KID, the queen's child, heard the human's call.
  • They brought the human back to the castle.
  • Over time, Monster Kid and the human became like siblings.
  • The King and Queen treated the human child as their own.
  • The underground was full of hope.
  • Then... One day...
  • The human became very ill.
  • The sick human had only one request.
  • To see the flowers from their village.
  • But there was nothing we could do.
  • The next day.
  • The next day.
  • ...
  • The human died.
  • Monster Kid, wracked with grief, absorbed the human's SOUL.
  • They transformed into a being with incredible power.
  • With the human SOUL, Monster Kid crossed through the barrier.
  • They carried the human's body into the sunset.
  • Back to the village of the humans.
  • Monster Kid reached the center of the village.
  • There, they found a bed of golden flowers.
  • they carried the human onto it.
  • Suddenly, screams rang out.
  • The villagers saw Monster Kid holding the human's body.
  • They thought that they had killed the child.
  • The humans attacked them with everything they had.
  • They were struck with blow after blow.
  • Monster Kid had the power to destroy them all.
  • But...
  • Monster Kid did not fight back.
  • Clutching the human...
  • Monster Kid smiled, and walked away.
  • Wounded, Monster Kid stumbled home.
  • They entered the castle and collapsed.
  • Their dust spread across the garden.
  • The kingdom fell into despair.
  • The king and queen had lost two children in one night.
  • The humans had once again taken everything from us.
  • The queen decided it was time to end our suffering.
  • Every human who falls down here must die.
  • With enough souls, we can shatter the barrier forever.
  • It's not long now.
  • Queen TORIEL will let us go.
  • Queen TORIEL will give us hope.
  • Queen TORIEL will save us all.
  • You should be smiling, too.
  • Aren't you excited?
  • Aren't you happy?
  • You're going to be free.

True Pacifist Route

Thanks to you, everything has fallen into place.
See you soon.
— Phone call in the True Lab's elevator

In the True Lab, the protagonist discovers that the first human and Monster Kid had worked together on a plan to get to the Surface and retrieve eight SOULS. While the human was on their deathbed, Monster Kid informed them they did not think it was a good plan anymore; ultimately, this leads to them betraying their sibling and aborting their plan.

After restoring the elevator's power, the protagonist receives a phone call from someone whose voice they have never heard before; the sound bite is similar to Momster Kid's.

After Temmie absorbs all monster SOULs and the six human SOULs, she transforms into Monster Kid.

Yo! <Name>, are you there?
It's me, your best friend.
— Monster Kid, before transforming into The God of Hyperdeath

Monster Kid greets the protagonist as <Name> before they transform into "MK DREEMURR, God of Hyperdeath." They inform the protagonist that they do not care about destroying the world anymore, and instead just want to reset the timeline so that everything unfolds again from the beginning. Monster Kid believes that the protagonist will continue even if they reset the timeline, because they want a "happy ending"

They then say that their first form is just a fraction of their real power and transform into their final form. Monster Kid reasserts that the protagonist will die in a world where nobody remembers them as their physical body fails them.

Maybe, with what little power you have...
You can SAVE something else.
— Narration before the SAVE option appears

The protagonist then calls to the Lost Souls inside Monster Kid's SOUL and reminds them that they are friends with the protagonist. After all Lost Souls regain their memories, the protagonist realizes that someone else needs saving. The protagonist calls their name, and a few sepia tone pictures display. The pictures are of Monster Kid and their sibling together when the human first fell into the Underground.

Monster Kid begins crying and reverts into their original form. After finding out that the protagonist's name is "Chara", Monster Kid tells them that the monsters really love them and apologizes for what they have done. They then return the human and monster SOULS, breaking the barrier.

They tell Chara that they have to go; Chara has the option to hug MK and comfort them before they leave. As they walk away, Monster Kid tells Chara to take care of their "parents" for them


  • Like Undertale Asriel, Monster Kid is made of every SOUL in the Underground during the battle.
  • Like Undertale Asriel, The First Human was their sibling and best friend.
  • Like Undertale Asriel, the protaganist can't hit Monster Kid during their battle.
  • While Undertale Flowey is actually Asriel, Underswap Temmie is actually Monster Kid.
  • It is widely believed that Monster Kid was going to be swapped with W.D. Gaster thanks to the existence of Goner Kid.
  • Not much is known about MK
  • MK is not a popular character in Underswap. Not much people talk about them.




Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.