Ah, the infamous reset...Now, they want to see what it's like to kill everything. Just because they can. And because they "can", they "have to".But it really makes me wonder...(WARNING: INCOMING TINFOIL HAT THEORY [AND POSSIBLE SPOILERS])What is the true antagonist of Undertale? Is it Flowey? Asriel? Chara? Personally, it doesn't seem like any of them are.Perhaps, on the genocide run, Chara is. But that's an exception.I think the antagonist, in some shape or form, is the very ability to save and reset. Somehow, it exists in a metaphysical way, and certain characters are aware of and/or able to manipulate it themselves. Flowey/Asriel resets so that way they can keep Frisk/Chara around forever. Sans USED to reset to try and save W. D. Gaster, but he gave up "a long time ago". Frisk/Chara resets in an effort to change the course of the underground's fate.However, at all times, somewhere, someone is resetting the game--regardless of their differing reasons. The characters all are ripped from the previous timeline back to the beginning of when Frisk falls down. Even then, some characters have brief moments of "deja vu", as if they've "seen/felt certain things before". Other characters have a higher sense of awareness over this, like Sans (due to his own ability/knowledge that is revealed in the Genocide run).So, perhaps, this ability to save/reset once never existed... Perhaps it was inadvertently created by something, or someone...Perhaps, when Gaster fell into his... experiments? or the CORE? (not sure which) and when he was torn apart into pieces scattered across space and time (becoming data itself, in a way), a link was established between the two. And with that link, those with the knowledge, ability, or connection could manipulate space and time itself, allowing them to "save and reset" the game.However...Sans couldn't save Gaster, no matter how many times he tried. Of course, that makes sense. After all, you can't reset to BEFORE when the incident occurred. The link between time and space that allows for the ability to save/reset NEVER EXISTED before Gaster was torn from reality. It can only be used to manipulate the time AFTER it was established. Perhaps this is what allowed some monsters of the past to have those visions of the "angel who has seen the surface" who either could save them all or kill them all?So as long as the ability exists... So as long as the link established (inadvertently) by Gaster's accident remains... Sans, and all the other monsters are doomed to be reset for all eternity.Now...What if there was a way to DESTROY that link...? What could Toby Fox be referring to when he said "the very nature of that [next] game is SHROUDED IN DARKNESS"?Hmm....

"ENTRY NUMBER SEVENTEEN

DARK DARKER YET DARKER

THE DARKNESS KEEPS GROWING

THE SHADOWS CUTTING DEEPER

PHOTON READINGS NEGATIVE

THIS NEXT EXPERIMENT

SEEMS

VERY

VERY

INTERESTING

...

WHAT DO YOU TWO THINK?"



...



You want to know what I think, Mr. Gaster? I think that we will be returning to the underground. It may be a long while from now, but we will be returning. But this time, we're coming to find you; we're coming to end your misery of existential pondering. And with that, we will find all of your pieces and destroy the link that you provide us. We will destroy the ability to save and reset once and for all. None of the monsters will ever have to worry about the timeline being reset ever again.



This will be the ultimate meta experience a game has ever given. A game that has a REAL end. An end where the player themselves lose their ability to replay the game... forever.