Chapter Text
Sans knows that he’s weak.
He also knows weakness in the underground is a death sentence. In a world where LOVE and EXP are the main currency of survival, being weak means easy pickings for other monsters looking to climb the ranks in the hierarchy of fear or be feared. An ambush would immediately dust him and his one-hit HP.
The obvious solution is to get stronger, to gain LOVE by killing other monsters first. It wasn’t as if Sans couldn’t hold his own in a fight when he was ultimately forced to. If he saw them coming, he could at least dodge or deflect the initial blow, and then strike back; but no, he had figured out that his HP hadn’t budged when he had finally gained a LOVE, that he was physically weak and too easily tired to actually ever improve.
The alternative is to live under another monster’s protection, in exchange for loyalty and obedience. It isn’t a shameful thing - plenty of monsters do it, just to cling to the semblance of security and to put food on their plates. Those in power were always in need for those who would bow to their power after all.
It isn’t shameful, but it is necessary, especially when Sans has Papyrus.
Fighting becomes much harder when he has Papyrus to defend. Although Papyrus is healthier and stronger than he ever will be, he is still so young, and still so very optimistic. He had clung onto the idea that if there was good in his brother, there was good in everybody, and had hesitated when he needed to harm another monster.
(And Sans, fool that he was, had let him think that way. Maybe he himself wanted it to be true.)
(In the future, Papyrus, well. Papyrus doesn’t believe in that anymore.)
So here’s the other secret, why they were still brothers in a world that laughed at the concept of ‘family’: Sans knows that he’s weak.
He’s weak for affection, for acts of tenderness and words of praise, for that elusive of concept of love. He wants the warmth of a hug, the touch of a gentle hand, the acknowledgement that he’s done something right, something well. He wants all that in a world that measured worth by LOVE, not love, and he knows that wanting something that has never existed is a little more than a foolish dream.
But oh, how he wants.
And maybe that’s why he doesn’t abandon Papyrus and open his eyes to the ways of the world - because Papyrus would never hesitate to tug at his arm and call him ‘brother’, to hug him after another day survived, to cry when he had almost got dusted. Papyrus is what keeps him going, what keeps him alive even though somedays he imagines it would be easier if he was dead - but what would happen to Papyrus if he died?
So when Gaster saves them from an ambush that they wouldn’t have survived, Sans accepts his offer to be his assistant, in exchange for food and lodgings for both him and Papyrus. He needs help to keep Papyrus alive and happy, and he’d do anything and everything for that.
The premises of his job is easy: do whatever Gaster tells him.
On good days, this means preparing experiments, fetching whatever the other skeleton needs, and cleaning up after the experiments. Sans finds that despite his lack of knowledge, the theories Gaster tests are frankly fascinating. He makes excuses to pore over the books in the library, trying to understand what the Royal Scientist is attempting, and sometimes even daring to affirm his understanding with Gaster himself by appealing to his arrogant side. On good days, Gaster even obliges, and Sans can pretend that the gleam in his eyes is one of pride.
It’s the experiments Sans is less enthusiastic about - but he has come to find that he prefers handling monster dust over preserved human remains, if only because they are easier to clean.
After work he trudges back to his quarters where Papyrus waits, bringing with him food and interesting items he thinks Papyrus would like. He had lied to Gaster that Papyrus was too young to read and be of any help in the labs, and that Sans himself would teach him. The other skeleton had nodded impassively, his face betraying no particular emotion and Sans had been thankful that he hadn’t had other… interests in Papyrus, something other Boss monsters might have demanded.
On bad days, Sans learns what obedience entails.
(Gaster did have interests. Just not in Papyrus.)
It starts small. Small, lingering touches on his arms; a phalange brushing against the back of his neck, catching briefly on the vertebrae. Sans stills, but Gaster never says anything, only continues with his next experiments.
The touches get longer, firmer - fingers pressing along the length of his collarbones, curling into the dip of his shoulder blade, Gaster stepping up behind him, leaning over him to reach for something on the shelf, drawing away with a lingering touch on his metacarpals. Whenever something falls onto the floor, he can feel Gaster’s gaze on him as he bends down to retrieve the item, intrusive and unsettling.
bear with it, Sans tells himself. There is nothing wrong with touching and looking. It’s better that these touches aren’t out to kill him. There’s nothing wrong.
So Sans keeps quiet when Gaster continues his ministrations, the touches only getting bolder. His palm drags down to the small of Sans’ back; his leg slides forward, resting against the back of Sans’ pelvis; his fingers curl around the jut of Sans’ hip as he crowds the smaller skeleton into a corner of the lab they worked in, experiment abandoned on the table.
“stop,” he finally snaps, his hand flying out to dislodge Gaster’s. Gaster removes his hand, but stays where he is. Though Sans is glaring right back at the older skeleton, he can feel how his back is pressing against the wall, see how unfazed Gaster’s gaze remains at his rejection.
“And here I’d thought you would wait until we were both naked,” the scientist says, his voice calm and measured and on this side of mocking. Sans bristles.
“i am not your personal whore,” he tells Gaster, because he didn’t sign up for this - and Gaster has the nerve to just laugh, an ugly bark that shows Sans exactly what he thinks about that.
“You’re supposed to do everything I tell you to,” Gaster repeats, his grin growing wide and wider. “Everything, including being ‘my personal whore’.“
He reaches for Sans again, and Sans reacts - he pings Gaster’s soul blue and throws him across the room, to get him as far away from him as he can, and runs towards the door of the lab. He has to get Papyrus out, they have to go - but just as Sans reaches the door, the cold grip of his boss’ magic on his soul slams him down onto the floor, just inches away from the door handle.
He hears Gaster standing up, brushing at his clothes, taking his own sweet time to saunter over to Sans’ prone body, held in place by magic without its master breaking a sweat. The footsteps stops, and the steady weight of a single foot presses down firmly onto the back of his ribs.
“That was the most stupid thing you could have done in your life,” Gaster says. Sans shivers at controlled anger beneath the smooth cadence of the other’s voice. “You’re usually so smart, Sans. You had potential, and that was why I saved you and your brother - but attacking me?” He tuts. "Perhaps I misjudged your intelligence.”
He struggles to get up, to throw Gaster’s magic off his soul - and Gaster grinds his foot sharply down, as if he was crushing an insect. Sans cries out, sharp and loud, and only then does Gaster lifts his foot.
“But perhaps I could allow this mistake,” Gaster says, his voice soft and deceptively gentle. “If this is to be the last time. What do you say, Sans?”
The grip around his soul eases ever so slightly, and Sans raises his head.
“if you’re going to kill me,” he snarls. “get on with it.”
“Kill you?” Gaster says. “Why would I do that?” There’s the sound of his lab coat dragging against the floor, and a boney hand brushes over the curve of his skull, as if he was being patted and if it weren’t so patronising Sans would have found it soothing. “You’re more useful alive to me.”
“i’m not letting you fuck me.“
The hand pauses, and then continues its repetitive motion. "What do you think would happen to your brother?”
The non sequitur was jarring, but the message is clear.
“don’t you fucking dare,“ and Sans begins to pull on the reserves of his magic, for the barest scraps in order to tear apart this bastard who would threaten Papyrus right here and right now, “you bastard, don’t you dare -”
The hand tightens around his skull in a crushing grip and slams it down onto the floor.
“Quiet,” Gaster is saying over the ringing pain in his head. Sans blinks profusely into the floor, his vision black and blurry, the dusty grey tiles of the laboratory swimming back into uncomfortable focus. “Let me tell you what will happen. You and your brother will be used as the test subjects in the next experiment. You will be the control, and watch while your brother receives the brunt of the testing. Then, later, I will, ah, fuck you, and use you however I like. Is that clear?”
Sans is going to kill him. Sans is going to gain a LOVE with this bastard’s death, and even Papyrus imploring him will not stop him.
“Or,” and the hand turns gentle, rubbing away at the pain, and Sans groans into the floor. “You let me take you, and I will continue keeping the both of you under my protection. I’ll even promise to not touch your brother. He can continue on living in blissful ignorance in your quarters, and you can pretend at his frankly nauseating ideas of world peace. But you and I know better than that, don’t we?
"And if you do manage to kill me,” Gaster laughs, low and dismissive. "Just think of how many monsters you have to fight off, and how many monsters would come after the both of you. Another challenger for the title of Royal Scientist. And another, and many, many more.”
The scientist stands up, and abruptly releases Sans’ soul from his hold. Sans stays on the floor, humiliated and defeated.
“I’ll be in my quarters,” Gaster says, turning his back to Sans. “Think about it, won’t you?“
He sweeps out of the room, and Sans does not move.