Note: This story utilizes a diverging timeline beginning at two different points. That means that after the starting point of this story, nothing will follow any future story of either UNDERTALE or Steven Universe. The Steven Universe story will start directly after the end of the episode "Bismuth," while UNDERTALE's story takes place about a year after the True Pacifist ending of UNDERTALE. Also, yeah, the UT crew's got an OC among them, but make of that what you will.

Everyone was moving kinda fast, and Steven was having a bit of trouble keeping up. Of course, this was just par for the course at this point, but he wished that the Gems would at least pause what they were doing for a second, just long enough to explain what was going on.

"Hey! Could you guys slow down for a second!"

No one paid any attention.

"C'mon, guys! What's going on?"

Despite Steven's pleading, everyone just kinda kept going. The Crystal Gems continuously moved back and forth, in and out of the temple and their rooms. Steven decided he'd had enough, and walked over to the temple gate, sitting down in front of it. When the door reopened and Pearl tried to exit, she almost tripped over the half-gem.

"Steven! What are you doing? Can't you see I'm busy?"

"Yes, I can! Which is why I need to know what you're doing!"

"Ugh. Steven, I…"

Pearl was silent for a few seconds before deciding that Steven would almost definitely just keep bothering her and the other Gems until somebody explained what was going on.

"Listen, Steven, it's not very important, but… it's complicated. The simplest way of putting it is that a whole lot of Gem technology has been acting up in ways that… we can't quite explain. The malfunctions extend to the equipment here in the temple as well, so we've got our hands full trying to get everything in control."

"That sounds kind of important. How can I help?"

"Right now, Steven, you can help by staying out of our way and letting us finish this. You're a capable fighter and a valued member of this team, but… you couldn't know less about Gem technology, and to be honest… we both know what happens when you try to interfere with magic."

"Eh. True enough. But you have to tell me when you figure something out!"

"Of course, Steven."

Frisk was worried. Sans had been spending a whole lot of time in his secret lab recently, and he seemed to have less and less energy every day. It also heavily weighed on Frisk's conscience that they knew what was going on, but they couldn't tell Papyrus. They had to fight their own DETERMINATION to keep lying to the poor skeleton. It went entirely against their nature to keep secrets like this.

But they'd promised Sans they wouldn't tell anyone, and they couldn't go back on that. They knew how important promises were to Sans. They knew from experience, and they could never forgive themselves if they betrayed his trust.

But it still hurt. Even though Sans liked to be alone as he worked on the machine in his lab, Frisk decided they should visit him. All things considered, it seemed like a pretty bad idea. At any time, they could head down there with him when no one else but the two of them were in the entire Underground. Unfortunately, the time they'd chosen to visit the lab was the same time that many of the monsters, as well as their half-human ally Iram, were visiting Ebbot for old times' sake.

Which meant that they were risking Sans' secrecy by visiting him. Nonetheless, Frisk was determined, and nothing was going to stop them from doing something they set out to do.

As Frisk stepped down into Sans' lab, they loudly announced their presence. 99.9% of the time, Sans was always on his guard, but when he was working on his machine he could be surprised, and he hated to be surprised.

"heya, kiddo. watcha doin' here?"

Frisk said that they were just there to check up on him, and to see if he was doing alright.

"welp, i'm fine. is that enough for ya?"

Frisk said it wasn't.

"no arguin' with ya, eh? well, guess that's to be expected from someone like you. howzit goin?"

Frisk said they were alright, but that they were worried about him. They said that he had been looking more and more tired each day.

"well, to be honest, i've been more and more tired. i've been workin' myself down to the bone down here, but i can't quit right now. this hunka junk has been actin' up, and i can't be sure what it'll do if i leave it alone."

Frisk asked why he didn't just deactivate it.

"ya can't just deactivate this baby, it doesn't work like that. it needs to always be runnin', or else the circuits inside it fry."

Frisk said that sounded like an absolutely horrible design choice.

"welp, at the time this was built, we hadn't designed transformers yet, so we had to pump all the energy something would need at any time into it at all times. so we also need a cooling system to constantly be active, or else… boom."

Suddenly, the large, rectangular machine in front of Sans began to beep rather consistently, and at a high pitch.

Frisk asked what it was.

"it says something's up, and i-"

The machine suddenly stopped and cooled down, all of the warning lights turning off.

"huh. that was easier than i'd expected. i was sure the timeline would be erased or something."

Frisk raised an eyebrow. ASRIEL hadn't been able to ERASE the timeline with them in it, so how could this machine do it? They weren't worried, not in the slightest bit, at least not about the timeline being destroyed. They were so determined that there was literally nothing they were afraid about killing them, it was their friends they were worried about. They hadn't SAVED since they left the Underground, on Sans' request, so if someone died, the absolute best they could do is reset everything that had happened since they beat ASRIEL. And that was not a good thing. But again, they'd made a promise to Sans.

And they would never break it, no matter what.

They asked Sans how the timeline could have been ERASED.

"well, it's complicated, but… long story short, that thing's a ticking time bomb. literally, a time bomb. it was originally meant to transfer a single person from one timeline to another, but it, uh, didn't work out that way. when it was first activated it literally took a chunk out of hotland. and, uh, it wasn't hotland at the time. as in, the machine opened up the earth and filled the area with lava. if it legitimately went off… the whole timeline could be ripped to shreds."

Frisk shuddered.

"yup. let's get outta here."

Frisk suddenly remembered that there were plenty of other monsters down here, and said as much.

"aha. i forgot too, they invited me to come with 'em. so… who's here, exactly."

Frisk said that everyone was. TORIEL, ASGORE, Undyne, Alphys, Papyrus, Iram, Mettaton, and Napstablook had all come.

"wonderful. well, i guess we'd better join up with 'em. maybe they'll believe us if we say we were just followin' along. here, i know a shortcut to the underground' exit."

Frisk followed along, and, just as Sans had said, they found themselves in the Last Corridor almost instantly. Moving deeper into the Underground, it wasn't long before they caught up to their allies, who were on their way out. Moving together, the monsters moved together toward New Home. But when they reached the Underground's exit, something was… different.

Frisk was the first one to comment, wondering why they… weren't in the Ebbot range anymore. Mt Ebbot, somehow, was now laying in an open green field.

"that's… not supposed to happen."

Papyrus started freaking out.

"WHERE ARE WE? WHERE ARE THE REST OF THE MOUNTAINS!? MOUNTAINS DON'T USUALLY MOVE, DO THEY!"

Alphys replied.

"N-no, they don't! T-this is not usually s-something that h-happens!"

Undyne clenched her fists.

"THEN SOMEBODY MOVED THE WHOLE FREAKIN' MOUNTAIN! Yeah! This is gonna be great!"

TORIEL spoke up.

"I do not believe it was a person that move the mountain, Undyne. It seems more reasonable that some magical force transported Ebbot away."

ASGORE rejoined.

"In that case, we must explain this. If we cannot, then we will surely be caught off-guard by what comes next."

Napstablook spoke next.

"if nobody minds, I've got a thought… what if-"

Mettaton interrupted him, shouting loudly.

"Wait! But what if we weren't moved at all? What if everything moved but us?"

"that's what I was going to say…"

Iram scowled at the both of them.

"None of that makes sense. It's obvious that it's the mountain that moved, not everything else."

"W-well, a-according to R-relativity, t-they're b-both the s-same thing."

"Whatever. But seriously, we can't have gone too far. Humans have pretty detailed maps. Let's just find a settlement, and then we can find out way back to Violet City and Ebbot."

"welp, sounds like a plan. hey, frisk, iram?"

"Yeah?"

Frisk asked what Sans wanted.

"so, have humans… changed since we last saw em?"

Frisk said they had, wondered aloud if Sans had seen them since.

"i was pretty sure i had, but… those ones don't look quite like humans."

Sans pointed a bony finger at a group not standing far from them. The four figures stood there, watching from a distance.

ASGORE crossed his arms.