"It's my duty to free us all......even if it leads to this....."
– StoryShift Sans
Sans is the lazy King of the Underground. He is said to be very lazy and he used to be good friends with Toriel Dreemurr, the Captain of the Royal Guard, until Toriel thought he tried to hurt a human whom he was only slowly setting down to save them from a fall. He needs seven human souls to break the barrier and free the monsters from Underground, same as his role's origin in Asgore and the determined king.
With everyone urging him to break the barrier, he keeps to himself in his home and throne room and is seldom seen outside of them. One of places he is most comfortable with is his throne, decorated with a pillow.
Sans wears some very pale pink slippers, grey sweatpants and an white t-shirt. However, he wears a big, blue cape with a cloak and silver pauldrons that have Delta Rune symbols. On the pauldrons, they have white fluff around the rim. He also wears a crown with red gems on it. On the cloak, it is grey on the corners.
Sans wears that purple robe that Asgore wears in regular Undertale and has a crown on his head. He still wears his blue jacket, black shorts, and pink slippers, shown when he destroys the Mercy button with the gaster blaster - under his robe.
Before Monster kind was trapped underground, King Sans was happy, living with his good brother Papyrus. After the war, he needed to kill 7 Humans, to obtain their SOULs and break the barrier to free the monsters. When Papyrus left him because of that plan, he grew depressed, and regretted his plan since he wants to see Papyrus again, but doesn't know that Papyrus occasionally regrets leaving his brother. He buys cheap noodles to make spaghetti on occasion.
He uses his regular bones instead of Asgore's fire, and he uses a Gaster Blaster instead of a trident. He will also turn the player's SOUL blue, and will dodge your attacks (since he only has 1 HP) until he gets tired. But he can't use KR (Karmic Retribution) due to the Protagonist (supposedly) has no LV, as KR only takes affect on those who have killed.
Papyrus met Chara one night when Chara, in a suicidal mindset, made their way to the Ruins door. They had intended to take their own life, but in their hesitation, they were overheard by Papyrus. Though at first Chara was quiet, the two soon began to speak to one another, Papyrus providing support to Chara and strengthening their resolve to protect their family.
It can be assumed that the two were very close, but after the deaths of Mettacrit and Napstablook, Papyrus left to the Ruins in order to spread their ashes and wound up staying there to watch out for any fallen humans. Papyrus would like to believe that Sans would do the right thing, but as time has passed, he's grown wary that Sans would and has killed the previous humans. However, unlike canon Toriel, he does not begrudge his brother and wants to forgive him.
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