So, first off, this isn't an official update to the story. Don't worry, though. I already have the next chapter planned out in my head. I just have to write it out and I will. Soon. Very soon.

This is just an explanation for the previous chapter and to kind of clear some things up. If you don't want to read this, that's fine. You can skip over this part completely. I will warn you, I might ramble on somewhat. And this definitely won't detract from the plot in any shape or form.

Still here? Okay.

Well, I came up with this theory. It's loosely based off the fact that monsters are made up and born of magic. Including Sans and Papyrus. Now, their magic isn't infinite, of course, thus, they replenish regularly with magic infused food stuff in the Underground. For instance, Sans' ketchup is imbued with magic and Papyrus' questionable spaghetti ingredients, are also infused with little quantities of magical essence. Every food item in the Underground has this magical quality, in other words.

Yeah, I know what you're thinking. For those of you who've played Undertale, this isn't news. Just hang on, I'm getting to the actual theory.

In the previous chapter, you can see Sans being affected by his magic. There's a good reason for this. He's a magical skeleton, conceived of magic. Just existing doesn't cause any harm per se, but, Sans, like any other monster, has to keep a daily intake of the magic food stuff I mentioned before. Because magic tends to deteriorate with time. To counteract this, monsters eat.

Also to satisfy hunger in most monsters' case, for preservation in Sans' and Papyrus' case. They're skeletons, after all. They can't get hungry. They don't have a stomach organ. But, the need is still there to eat.

Or else they suffer withdrawal symptoms as their bodies need magic to survive. Such as weakness, fatigue, pain. Much like Sans experiences in Fatal Mistake.

Running with the logic that monsters are made of magic and they can't just pull magic out of thin air, -for the world's magic is too limited to manipulate like that-, Sans is directly drawing on the magic holding him together to summon bones. Which is highly dangerous. Hence the excruciating pain and then exhaustion that sets in toward the end.

As for the dimensions distorting and the world changing color... I like to think that if Sans' left eye changes color due to a sudden influx of magic, that it would have an immediate impact on his overall view of his surroundings.
Such as everything behaving strangely and everything's washed in cyan due to the outpour of magic through his left eyesocket.

Mm, I think that about covers it.. Hope all that made enough sense. If you decided to stick around, thank you for reading. Remember to vote if you enjoyed. Comment if you'd like to leave feedback. Until next chapter!
-J