Sans is the brother of the 9th human. He serves as the final boss of the True Pacifist Route.
Sans is a short skeleton with a dimpled smile and large orbits. He wears a blue shirt, black pants with white stripes, and a pair of sneakers/slippers.
God of Bad Time
The form is named directly in Truetale, where the [Check] option labels Sans as "the absolute GOD of Bad Time!"
He wears a long, dark robe with white sleeves and the "Knife God" on the front. This robe is similar to Flowey's but it's longer. He also wears a locket similar to the Bone Locket.
Sans's body becomes more geometric, and his teeth get sharper. He has a pair of blue wing, and his lower body becomes sharp and Heart-shaped.
While this form is not directly named, it resembles the "Knife God", which looks like the "Skeleton Of Bad Time" from the prophecy.
Before his death, Sans was a docile, unadventurous, and loving child. He cared for the 9th Human as a sibling, and he trusted them when they came up with a plan to escape the Underground that involved them consuming buttercups.
After Frisk resurrects Sans without a SOUL as Socky, he becomes incapable of feeling love. This makes him bored and resentful.
After temporarily regaining his compassion, he apologizes for his actions to Mettaton and realizes the gravity of his actions as a sock.
Truetale, Sans found the fallen human, who was the 9th human to fall into the Trueground. They became his adoptive brother and best friend. Just before the human died, their last wish was to see the golden flowers of their village, on the Surface. Sans absorbed their SOUL, and the human carried their own body across the barrier to their home village. Sans and his brother shared control of Sans's body after their SOULs had combined.
The villagers assumed that the Sans/Human fusion had attacked and killed the human child. The Sans/Human fusion did not fight back but only fled. Lethally wounded, the Sans/Human returned to the Underground and died. Once deceased, Asriel's body turned to dust, which spread across the garden in New Home.
Later, just before the prince left, Frisk injected determination into one of the socks. Initial experiments on the sock vessel proved unsuccessful, and Frisk returned it to Chara. Once Frisk replanted the vessel, Socky awoke within the garden.
Though Sans's essence from the garden bed granted Socky Sans's memories. He did not have a SOUL and thus could not feel love, joy, or compassion.
Sans does not appear during a Neutral Route.
However, when the protagonist falls into the Garbage Dump, the protagonist hears Sans's sound bite during a memory from Sans's human brother. Monsters also tell the story of Sans and the 9th human during the walk in New Home.
The Story of Sans and The 9th Human
This is the story told by monsters at the end of a Neutral Route. The song "Truetale" plays during this sequence.
A long time ago, a human fell into the RUINS.
Injured by its fall, the human called out for help.
Sans heard the human's call.
He brought the human back to the castle.
Over time, Sans and the human became like brothers.
The trueground was full of hope.
Then... One day...
The human became very ill.
The sick human had only one request.
To see the flowers from their village.
But there was nothing we could do.
The next day.
The next day.
The human died.
Sans, wracked with grief, absorbed the human's SOUL.
He transformed into a being with incredible power.
With the human SOUL, Sans crossed the barrier.
He carried the human's body into the sunset.
Back to the village of the humans.
Sans reached the center of the village.
There, he found a bed of golden flowers.
He carried the human onto it.
Suddenly, screams rang out.
The villagers saw Sans holding the human's body.
They thought that he had killed the child.
The humans attacked him with everything they had.
He was struck with blow after blow.
Sans had the power to destroy them all.
Sans did not fight back.
Clutching the human...
Sans walked away.
Wounded, Sans stumbled home.
He entered the castle and collapsed.
His dust spread across the garden.
The kingdom fell into despair.
The humans had once again taken everything from us.
The king decided it was time to end our suffering.
Every human who falls down here must die.
With enough souls, we can shatter the barrier forever.
It's not long now.
Queen CHARA will let us go.
Queen CHARA will give us hope.
Queen CHARA will save us all.
You should be smiling, too.
Arent you excited?
Arent you happy?
You're going to be free.
True Pacifist Route
In the True Lab, the protagonist discovers that the 9th human and Sans had worked together on a plan to get to the Surface and retrieve six human SOULs. While the human was on their deathbed, Sans informed them he did not think it was a good plan anymore; ultimately, this leads to him betraying his brother and aborting their plan.
After restoring the elevator's power, the protagonist receives a phone call from someone whose voice they have never heard before; the sound bite is similar to Sans's.
After Socky absorbs all monster SOULs and the six human SOULs, he transforms into Sans.
Sans greets the protagonist as <Name> before he transforms into "SANS THE SKELETON, God of Bad Time." He informs the protagonist that he does not care about destroying the world anymore, and instead just wants to reset the timeline so that everything unfolds again from the beginning. Sans believes that the protagonist will continue even if he resets the timeline because they want a "happy" ending.
He then says that his first form is just a fraction of his real power and transforms into his final form. Sans reasserts that the protagonist will die in a world where nobody remembers them as their physical body fails them.
The protagonist calls to the Lost Souls inside of Sans's SOUL and reminds them that they are friends with the protagonist. After all Lost Souls regain their memories, the protagonist realizes that someone else needs saving. The protagonist calls their name, and a few sepia tone pictures display. The pictures are of Sans and his brother together when the human first fell into the Underground.
Sans begins crying and reverts to his original form. After finding out that the protagonist's name is "Mettaton," Sans tells them that the monsters really love them and apologizes for his actions. He then breaks the barrier.
He tells Mettaton that he has to go; Frisk has the option to hug Asriel and comfort him before he leaves. As he walks away.
Sans is at the flowerbed in the Ruins. Mettaton only encounters him immediately after his boss fight; if the player watches the True Pacifist Ending Credits and reloads the game, Sans does not appear. Sans speaks extensively to Frisk and offers them a different philosophy than his flower counterpart: "Don't kill, and don't be killed." He also mentions to be careful on the Surface because "there are a lot of Sockys out there."
Sans's Epilogue Dialogue
Don't worry about me.
Someone has to take care of these flowers.
Mettaton, please leave me alone.
I can't come back.
I just can't, OK?
I don't want to break their hearts all over again.
It's better if they never see me.
... why are you still here?
Are you trying to keep me company?
Let me ask you a question.
Why did you come here?
Everyone knows the legend, right...?
"Travelers who climb Mt. Ebott are said to disappear."
Why would you ever climb a mountain like that?
Was it foolishness?
Was it fate?
Or was it...
Only you know the answer, don't you...?
I know why <Name> climbed the mountain.
It wasn't for a very happy reason.
I'll be honest with you.
<Name> hated humanity.
Why they did, they never talked about it.
But they felt very strongly about that.
You really ARE different from <Name>.
In fact, though you have similar, uh, fashion choices...
I don't know why I ever acted as if you were the same person.
The truth is...
<Name> wasn't really the greatest person.
You're the type of friend I wish I always had.
So maybe I was kind of projecting a little bit.
Let's be honest.
I did some weird stuff as a flower.
There's one last thing I feel like I should tell you.
Mettaton, when <Name> and I combined our SOULs together...
The control over our body was actually split between us.
They were the one that picked up their own empty body.
And then, when we got to the village...
They were the one that wanted to...
... to use our full power.
I was the one that resisted.
And then, because of me, we...
Well, that's why I ended up a flower.
This whole time, I've blamed myself for that decision.
That's why I adopted that horrible view of the world.
"Kill or be killed."
After meeting you...
Frisk, I don't regret that decision anymore.
I did the right thing.
If I killed those humans...
We would have had to wage war against all of humanity.
And in the end, everyone went free, right?
I still feel kind of sad knowing how long it took...
... so maybe it wasn't a perfect decision.
But you can't regret hard choices your whole life, right?
Well, not that I have much of a life left.
But that's besides the point.
Mettaton, thank you for listening to me.
You should really go be with your friends now, OK?
Oh, and, please...
In the future, if you uh, see me...
Don't think of it as me, OK?
I just want you to remember me like this.
Someone that was your friend for a little while.
Oh, and Mettaton...
Be careful in the outside world, OK?
Despite what everyone thinks, it's not as nice as it is here.
There are a lot of Socky out there.
And not everything can be resolved by just being nice.
Don't kill, and don't be killed, alright?
That's the best you can strive for.
Well, see you.
Don't you have anything better to do?
After the credits sequence, when reopening the gam . Sans returns as Socky and begs <Name> to "Let [Mettaton] go" and allow everyone to live their lives.
After the protagonist kills Flowey, Socky tells them that they are not really human, and mistakes them for the 9th child, telling them that they are still inseparable after all those years.
When the protagonist reaches New Home, Socky welcomes them and discusses his backstory as a sock and how he discovered his ability to SAVE. Near the end of his dialogue, he realizes that the protagonist will not hesitate to kill him, and he is frightened for his life. He rescinds his previous plans with the protagonist and tells them to leave him alone.
Socky's Genocide Route Dialogue
Heya, <Name>! You finally made it home. Remember when we used to play here? Heh... Boy! Today's gonna be just as fun.
I remember when I first woke up here, in the garden. I was so scared. I couldn't feel my arms or my legs... My entire body had turned into a sock! "Flowey! Chara! Somebody help me!" I called out. But nobody came.
Eventually, the queen found me, crying in the garden. I explained what had happened to him. Then he held me, <Name>. He held me with tears in his eyes, saying... "There, there. Everything is going to be alright." He was so... Emotional. But... For some reason... I didn't feel anything at all.
I soon realized I didn't feel ANYTHING about ANYONE. My compassion had disappeared! And believe me, it's not like I wasn't trying. I wasted weeks with that stupid queen, vainly hoping I would feel something. But it became too much for me. I ran away from home.
Eventually, I reached the RUINS. Inside I found HE, <Name>. I thought of all people, HE could make me feel whole again. ...
He failed. Ha ha...
I realized those two were useless. I became despondent. I just wanted to love someone. I just wanted to care about someone. <Name>, you might not believe this... But I decided... It wasn't worth living anymore.
Not in a world without love. Not in a world without you. So... I decided to follow in your footsteps. I would erase myself from existence. And you know what? I succeeded.
But as I left this mortal coil... I started to feel apprehensive. If you don't have a SOUL, what happens when you...? Something primal started to burn inside me. "No," I thought. "I don't want to die!" ...
Then I woke up. Like it was all just a bad dream. I was back at the garden. Back at my "save point."
Interested, I decided to experiment. Again and again, I brought myself to the edge of death. At any point, I could have let this world continue on without me. But as long as I was determined to live... I could go back.
Amazing, isn't it, <Name>? I was amazed, too.
At first, I used my powers for good. I became "friends" with everyone. I solved all their problems flawlessly. Their companionship was amusing... For a while.
As time repeated, people proved themselves predictable. What would this person say if I gave them this? What would they do if I said this to them? Once you know the answer, that's it. That's all they are.
It all started because I was curious. Curious what would happen if I killed them. "I don't like this," I told myself. "I'm just doing this because I HAVE to know what happens." Ha ha ha... What an excuse!
You of all people must know how liberating it is to act this way. At least we're better than those sickos that stand around and WATCH it happen... Those pathetic people that want to see it, but are too weak to do it themselves. I bet someone like that's watching right now, aren't they...?
Nowadays, even that's grown tiring. You understand, <Name>. I've done everything this world has to offer. I've read every book. I've burned every book. I've won every game. I've lost every game. I've appeased everyone. I've killed everyone. Sets of numbers... Lines of dialog... I've seen them all.
But you... YOU'RE different. I never could predict you, <Name>.
When I saw you in the RUINS, I didn't recognize you. I thought I could frighten you, then steal your SOUL. I failed. And when I tried to load my save file... It didn't work.
<Name>... Your DETERMINATION! Somehow, it's even greater than mine!
I just have one question for you, <Name>. How did you get back to the RUINS from here...?
... wait, I know. He must have taken you when he left. And decided to give you a proper burial, rather than... Hanging out in the basement forever. ... but, why then...? What made you wake up? Did you hear me calling you...?
It doesn't matter now. I'm so tired of this, <Name>. I'm tired of all these people. I'm tired of all these places. I'm tired of being a flower. <Name>.
There's just one thing left I want to do. Let's finish what we started. Let's free everyone. Then... let's let them see what humanity is REALLY like! That despite it all... This world is still "kill or be killed!!"
Then...? Well. I had... Been entertaining a few ways to use that power. Heh... ... But seeing you here changed my mind. <Name>... I think if you're around... Just living in the surface world doesn't seem so bad.
We don't even need to leave to get them this time. The queen has six of them locked away. I've tried hundreds of ways to get him to show me them... But she just won't. <Name>... I know he'll do it for YOU.
Why am I telling you all of this? <Name>, I said it before. Even after all this time... You're still the only one that understands me. You won't give me any worthless pity!
Creatures like us... Wouldn't hesitate to KILL each other if we got in each other's way. So that's... So... that's... Why...
... heh... Heh... ... what's this... feeling? Why am I... Shaking? ... Hey... <Name>... No hard feelings about back then, right? ... H-Hey, what are you doing!? B... back off!!
I... I've changed my mind about all this. This isn't a good idea anymore. Y-you should go back, <Name>. This place is fine the way it is!
... S-s-stop making that creepy face! This isn't funny! You've got a SICK sense of humor!
After the protagonist defeats Asgore, they easily kill Chara. Socky destroys Asgore's SOUL and pledges himself to the protagonist one final time in an attempt to save his own life, revealing his true identity as Sans in the process. He cries and begs the protagonist not to kill him, to no avail.