[Undertale] Sans X Reader - Repeat, Eternally

Chapter 33 ~ Gaster, of What The Hell He's Been Doing

Gaster sighed, a skeletal palm scratching against his face. He had lied to you, and no doubt hurt you. But he made it right. He fixed it.

But his son may never talk to him again.

"Sans." He had said. "Sans, they need you." 

"No, they don't. They said they didn't." His voice was dead. Gaster had never expected to hurt his little boy so much, and it was breaking his heart. He thought it would fix them both, but they couldn't live without one another.

"Sans, she's going to die out there. The alternate you..."

"What?!" His voice was much more alive now.

"I lied. Asriel took their form. An illusion. We did it to protect you both. So please... go back to them. Do something. Save them." 

"...Why don't you?" 

"...Because I can't face them. I don't think I ever can again. All I can do is make some calls, get everyone together... and fade away into the background." Gaster laughed sorrowfully. "Like...like I always have." 

"No... Dad, you can't..."

"Admit it, Sans. I've been a terrible father. I sacrificed my life for a person I barely knew, abandoning you in the process. I've allowed you to fall irrevocably in love with them, and ended up going so far as to use them as a sacrifice to save everyone else. Even at the end, I still... I still ended up screwing up. I still managed to separate you."

"But...there's always a chance for a new beginning." 

"You don't understand, Sans. It always resets. It always happens, just like this." 

"Wha...reset? What are you talking about?" Sans laughed nervously. "We're not stuck in the timelines anymore, dad. You're goin' a little crazy, there." 

"Sans... this isn't the first time you've all done this. Don't you remember? None of you do. None of you... not even them. This happens over, and over, and over, and over, and over and all I can do is be a pawn. All I can do is urge them back to life, every RESET. It's a set course. I know what I'm doing, and I can't stop myself. If I disappear, maybe the Pillars won't show up. If I disappear, maybe they won't RESET. Maybe... Maybe everything will be okay this time around."

"Old man...how long...?" Sans whispered.

"Eternity, Sans. There's no time limit. There's none at all. We're all just trapped here. There's no escape, my child. No matter what we can do, we're only just puppets. We're all just THEIR puppets."

"Who is they!?" Sans asked. No use. The line went dead. Sans dreaded the feeling in his heart. What did his father mean by Pillars?