Sanser is from CancerTale. He was formerly a human in this AU.
As a human, Sanser developed stage 4 bone cancer from looking at the Undertale Fandom. This killed him, but he was revived due to pure spite against the fandom for bastardizing him so much. He then set out on a mission to give everyone cancer.
After he was revived, he met Flowey. He shook his petal, but this killed Flowey. He realized he had the power to give any living being cancer. His journey is identical to Undertale's genocide run until he leaves the ruins, where he meets Papyrus. When he met his brother, he was reminded of the good in this world. He stopped giving monsters cancer. He lives with Papyrus, but they accidentally touched, giving Papyrus cancer.
Papyrus died six weeks later. In Sanser's rage, he ran through Snowdin, cancering every monster in sight. Undyne tried to stop him, but Sanser killed her with the knife he had stolen from Toriel. He went into hiding after this.
A week later, Frisk fell into the underground. They wandered through the ruins, but found only corpses. The sole survivor, a Froggit, warned Frisk of Sanser, before succumbing to his cancer. Frisk took a knife from Toriel's drawer, and ventured out of the ruins.
Sanser stood in the forest, and encountered Frisk. He told Frisk his story, of how the fandom did this to him. He told Frisk that out of everything he now hates about this world, he hates himself the most. Because of what the fandom did to him. Because of what the world did to him. Because of what he did to others. He then prepared for battle.
Sanser attacks Frisk with his knife, hesitant to give them cancer. They dodge, and try to talk to him. He reveals his motivation, to use Frisk's soul to escape the underground and give the Undertale fandom cancer. He finally gets Frisk down to 1 HP, and is about to give them cancer, but he cannot. He hesitates, breaking down in tears. He can never save the fandom. He can never save his own soul. Frisk hugs him, but notices Sanser has given himself cancer. It spreads rapidly, and as he turns to dust, he says "I guess there are some good people in this fandom...and I know I wasn't one of them..."
Frisk then takes Sanser's jacket, puts it on, and faces off against Asgore, sparing him. They break the barrier using Sanser's soul, freeing what remains of monsterkind.
Sanser attacks Frisk, but when Chara attacks, they don't dodge. He is stabbed, and reveals his backstory. He then welcomes death, saying "heh...there's no Undertale fandom in hell, no matter how many sins they commit..." before turning to dust.
Chara continues Sanser's idea of exterminating the Undertale fandom on the surface. They almost succeed, but as soon as they try to kill their first target, it tries to talk about Undertale with what it thinks is a cosplayer. This gives Chara cancer, and they die.
Sanser, unlike other versions, is evil. He wishes to commit genocide, but rather than quickly killing everyone he wants their deaths to be as painful as possible. Before he died, he was a shy and quiet human. He began to change as he watched the fandom of his favorite game deteriorate. When he died, he was so vengeful that he had enough determination to revive him as a skeleton.
Sanser hates the Undertale fandom for ruining his favorite game and killing him.
Sanser wears an outfit similar to his Undertale outfit, but dustier and torn in several places. He lost his right arm below the elbow to bone cancer. His eyes' pupils are usually small and green, but in battle they flash bright green similar to his Undertale fight.
- Cancer cell manipulation - Sanser can cause any living being to develop cancer. He can give them cancer on any part of their body, and at any stage. He can give people cancer that goes from stage 1 to terminal in seconds.
- Speed - Like all versions of Sans, Sanser is fast enough to dodge attacks.