* Ahuhuhu~
* This page needs tidying up, my deary~
* After all, unfortunate things happen to messy places.

To meet the UTAU wiki's quality standards, this article may require cleanup. Please help by improving the article.

* Do not edit this page without NovaHeart8's permission.

About the AU

A written AU created by NovaHeart8 and SwapTale10.

The description is as follows: "Through DETERMINATION, the promise was carried out.

An Undertale AU in which everything, overall, goes right. The game of Undertale (spoiler warning) but with emotional twists. Disclaimer: Most dialogue, and all characters, belong to Toby Fox.

Trigger warnings will be used at the beginning of the chapters affected. "

(Everything going right is a matter of opinion, of course.)

Frans does become canon in this AU, but this will not take place until much later.

The author is NovaHeart8, editor is SwapTale10.

AU Synopsis*

After multiple resets, Frisk collects pieces of Gaster's soul, which combine to bring him back to life. Once this happens, Frisk frees Gaster from the Void. Frisk returns to the Surface, then takes their own life to defeat Chara, who would have otherwise possessed them due to a deal they made at the end of a Genocide run. They reset just as they die, forever trapping Chara in their fallen body, and putting everything back in its place. However, Gaster remains alive, and a new Frisk enters the Underground.

This story puts an emphasis on the power of promises and trust, especially the promise Frisk made to their late mother that they would stay determined and fulfill their dream of exploring the world, helping others in the process.

As Frisk travels through the Underground, they realize that the impact of their choices- and their words- is far greater than they could have ever imagined.

*: This synopsis will be updated at a later date.



Main Protagonist:


Secondary Protagonists:





Major Characters:

With a Point of View*:







Without a Point of View:

-Gaster Follower #1**

-Gaster Follower #2**

-Gaster Follower #3**


Other Characters:

Any other character in Undertale is included in this story also. This includes Goner Kid.

Additional Information About Characters:

*: All P.O.V.s are third-person limited.

**: The Gaster Followers have been given names depending on what character they are based off of or their character traits. Gaster Follower #1 is named "Ficus" since his sprite closely resembles that of the Ficus Licker character met in the restaurant at MTT Resort. Gaster Follower #2 is named "Rhyme" since he speaks in rhyming couplets. Gaster Follower #3 is named "Smile" since his sprite is a smiling head.

Major characters enter the story one at a time. Those without a Point of View do not arrive until much later in the story.

The ages of the characters are as follows:

-Frisk is 15/16

-Sans is 19

-Papyrus is 18

-Gaster is 37*

-Flowey/Asriel is 20

-Toriel is 50

-Asgore is 51

-Undyne and Alphys are 24

Ages will be added as characters are introduced, and are subject to change. However, they most likely will not.

The ages listed are the ages of the monsters in human years. Monsters age differently than humans. For example, Asgore is at least 100, but in human years, he is only 51.

*: Gaster stopped aging when he was in the void, since he was stuck in time.

Additional Information

This story is currently in progress. Chapters are available on both and

SwapTale10 is uploading chapters to DeviantArt.


-PromiseTale was once a roleplay.

-This AU was inspired by GlitchTale. (The story is, of course, completely different.)

-Although Frisk is a "they" in this AU as they are in canon, they are much more feminine.

-Frisk wears faded grey pants in this story rather than shorts as in canon.

-Gaster is very kind in PromiseTale since there are rarely any AUs in which he's not made into an abusive villain.

-All characters (except Napstablook) have an affinity for acting, though never mentioned in the story.

-The author makes an appearance in the second-to-last chapter. The notebook she's writing in is passed on to Frisk at the end of the epilogue.

-If there was already a popular AU named "PromiseTale", then the name of this AU would have been "UnderVow".

-The Intro of the story, which was removed from FFN due to not following content guidelines (but is still available on Wattpad), was created to pay homage to the story's origins as a roleplay.

-Frisk has only minor allergies to Temmies. Meaning, they may sneeze when they're around one, but nothing more.

*:This list will be updated as the AU goes on.