Checkverse
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Summary
Undertale was famous across the Multiverse.
The copies however…they were less notable. Those that grew as timelines to split off into AUs of their own right were known, yes, of Dusttale and Horrortale and Aftertale and the curiously named Something New, but rarely would a single copy stand out.
Except one. Infamously banned from ever being touched by Multiversal interference, an unstable AU that had experienced so many timelines that the RESET was glitched, causing the Sans within to live through Dusttale and Something New. But when those timelines reached the same point that the originals had multiversal interference, the RESET button malfunctioned and sent them all back to the original Undertale timeline, only the equally glitched Sans beyond its influence.
But this story is not about the Multiverse at large, not a single SOUL dared to touch the absolute mess that was Undertale#297. Yet in the heart of that mess, its final timelines began to unfold; the consequences of tragic history not remembered, the results of what it had wrought upon its sole survivor.
Series
- Part 1 of Checkverse
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Summary
(desc too long for ao3 oops)
Undertale#297. Glitched, unstable, banned from ever being contacted by Multiversal visitors out of fear that it could get worse. But no one considered that the Sans within would reach out. It was rare for an AU to figure out AU travel by itself, after all.
And yet, Check figured it out. But to jump immediately into a Multiverse with no sure way back and no knowledge of its happenings? No, he had a proclivity towards impulsivity, but he wasn't an idiot. Measure once, check twice, after all. So he took his time. Figured out how to target the portals, learned how to return home, refined and slimmed his design down until it was handheld, and most of all, he learned the politics of the Multiverse.
But something about it didn't sit right with him. He'd been Dust and he'd been Killer, so why were Dust and Killer spreading "senseless" negativity? He didn't know, but honestly…he didn't care.
He saw his copies, and his only thoughts were those of mischief. It was an awful idea, and he'd definitely get hurt, but…
Well, a bit of harmless impersonation was always fun.
Or; Check travels universes for the lolz and indirectly stops an eons-long war by doing almost nothing
Series
- Part 2 of Checkverse
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Summary
The two hundred and ninety seventh copy of the Original variant, Undertale, started off much like its origin. Long ago, humans and monsters lived in harmony. Then, war tore the lands, and the humans were victorious, sealing the monsters underground with a magic spell. Only the power of seven human SOULs would shatter the barrier.
Time passed, seven humans fell, six SOULs gathered, and it was Fate that a child would determine Destiny through DETERMINATION. And so the story goes.
But no copy is perfect, least of all this one.
Aren't you…curious?
How did this world diverge?
What happened here?
Why was Fate woven so?
And…who, exactly, was Sans? Dust? Killer?
When did he change from one to another…? (Or maybe, just maybe, he was always himself.)
Or; look i was writing bad sanses + star sanses backstory fics i might as well make one for check as well
Series
- Part 3 of Checkverse
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Bad At SOUL (But Sweet At Heart) by BlazingFieryMountain
Fandoms: Undertale (Video Game)
01 Nov 2025
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Summary
Filled with LOVE and love. DETERMINATION and HATE. Hope and despair. Willing or not, they ended up in Nightmare's Gang.
In modern days, they hold each other close and bear the brunt of the pain for each other.
But they didn't start out that way. Nothing close to it at all. No, despite their care they hold now, nothing would change their origins, of blood and dust and pain and HATE and LOVE and violence.
This is that story, of how their LOVE softened into love, how painful beginnings beget kind endings all the more sweet for their suffering.
Or; How Nightmare's gang got recruited, and a cruel dictator became a patient parent of four. (Bad Sanses recruitments/backstories.)
Series
- Part 4 of Checkverse
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Summary
(shortened desc - i made the og too long again lol whoops :P)
Dust hated Killer. He hated his stupid smirk, and her teasing words, the stupidly casual tricks with knives. The way Killer was so effortlessly pretty. His empty eyesockets, holding space for galaxies within, her quiet excitement when his SOUL was more normal and she could feel again, his gentle touch as she bandaged Dust's wounds. Dust hated Killer.
Killer hated Dust. He hated his smug grin, and his inane ramblings, the stupidly casual display of his insane magic control. The way Dust was so effortlessly pretty. His shining eyelights, DETERMINATION blazing within, his quiet excitement on kinder days when his past did not haunt him quite as fiercely, his careful touch as he wiped away Killer's tears. Killer hated Dust.
And yet still SOULs fluttered despite genuine frustration. Self hatred directed onto someone so much like themselves, for they were once the same. Everyone dead. Torment. Genocides. And somehow, despite it all, a hand to hold. So what if they got their hands a little dusty?
(Canon to Checkverse. Technically can be read as a standalone, but looks at you with my big sad eyes please pleaseeee read my fics)
Series
- Part 5 of Checkverse
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Summary
"LOVE, too, is an acronym. It stands for "Level of Violence." A way of measuring someone's capacity to hurt."
Even the pull of time itself would not be enough to run away from his willingness to cause pain.
"The more you kill, the easier it becomes to distance yourself."
His count surely lay in the hundreds of thousands by now, almost a century's worth of endless slaughter, over and over and over. So distant he was just an observer as his body continued its muscle memory of murders.
"The more you distance yourself, the less you will hurt."
Only numbness lay in his SOUL. Emotional, physical, mental, all of it was nothing, unless experiencing the rush of EXP, the gain of LOVE.
"The more easily you can bring yourself to hurt others."
He didn't want to. But it wasn't hard to turn to it, when a kid stumbled out of the ruins covered in dust.
Or; Noncanon what-if, where LOVE sticks through Total RESETs, and Sans doesn't have any sense of impulse control.
(i wrote this while listening to https://youtu.be/qT7c8hk73kY?si=GD_G4kmyhUu-tQJu, banger song btw you should also loop it for days on end like me)Series
- Part 6 of Checkverse
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Summary
This entire tale has been told through one frame of vision.
Perhaps you would like to know a little more? Get a glance into the minds of those involved.
(Or; Alternate POVs to existing scenes in the story. Thank you Daoist_Popcorn for the fic concept :D)
(All chapters in this fic prone to occasional edits due to typos and various other mistakes + ideas)
Series
- Part 7 of Checkverse
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Round The Rumour Mill (Placeholder Title) by BlazingFieryMountain
Fandoms: Undertale (Video Game)
14 Aug 2025
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Summary
...Haven't you heard?
Didn't you see?
Don't you know?
The Gang, the Stars, this specific string of universes…
And so the tale spreads. Often inaccurate, but occasionally holding a nugget of truth.
Here are a few of those rumours. You can guess for yourself just where they came from, and how truthful they are.
(Requested by WildfireXx)
Series
- Part 8 of Checkverse
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Summary
"He opened several portals in rapid succession[...]even Dusttale#6 for good measure[...]He swore he saw a flash of surprised red eyelights somewhere in that sequence, but eh, that probably would never be relevant to him."
No, it wouldn't be relevant to Check. Nor the Multiverse he dwelled in, not significantly. But that one moment brought DETERMINATION back to the Sans of Dusttale#6, Helvetica. He'd thought his universe cut off from the Multiverse, after losing connection to Underfell#143, when his Universe's code changed from Undertale to Dusttale.
But now, he believed different. He could get Carmine back, despite how much he had changed. Then they could find a way to flee to a different Multiverse altogether, free of the bounds of their Universes, because surely that was what that sight was. A version of himself who had learned to hop Multiverses.
Or; Butterfly effect. (This is a backstory piece to a potential future series. Does include established Dustard/Dustfell. This [unnamed] universe will have more shippy stuff than Checkverse {and is also technically my excuse to show off some of my fav rarepairs})
(VERY much a warmup piece for this AU, shorter than my regular stuff :P)
Series
- Part 9 of Checkverse
- Part 1 of Placeholder Title (The Multiverse Crossover Fics)
- Language:
- English
- Words:
- 1,478
- Chapters:
- 1/1
- Kudos:
- 6
- Hits:
- 82