---
*Chapter 1: The First Fracture*
The Underground was always chaotic, but never like this. It started with whispers—monsters acting strangely, eyes glowing with unnatural rage. At first, Sans ignored it. Weird stuff happened all the time down here. But when **Toriel** attacked *without hesitation*, he knew things had gone horribly wrong.
"Get inside, Papyrus," Sans muttered, watching the once-gentle queen claw at the air, her SOUL flickering erratically.
"But—" Papyrus started.
"Now."
Papyrus retreated, leaving Sans standing alone in Snowdin's bitter wind. He took a slow breath, eyes narrowing. Something had taken hold of the Underground. The monsters weren't themselves anymore. Whatever it was, it wasn't natural.
**And it was spreading. Fast.**
---
### *Chapter 2: Immune but Not Unscathed*
Sans and Papyrus realized it first—**the infection didn't touch them.** The virus, whatever it was, spread through magic, flesh, and SOUL signatures. But skeletons? They had no flesh. No nerves to infect. So while the entire Underground fell into madness, they remained untouched.
The human, meanwhile, clung to something stronger than biology—**Determination**. That sheer force of will was like a barrier, keeping them sane even as the world around them burned.
But being immune didn't mean being safe.
Every friend Sans had was now an enemy. Every monster he once laughed with was now a hunter. He wasn't sure how much time was left before even the human's resistance broke.
And then there was Papyrus.
"I WON'T FIGHT THEM," Papyrus declared, arms crossed.
"They're gonna fight you," Sans replied, keeping his voice neutral.
Papyrus shook his head. "THEN I'LL SAVE THEM."
Sans sighed. He wanted to believe in miracles, but survival wasn't about belief—it was about action. And if he didn't do something, they'd all be dust by the end of the week.
---
### *Chapter 3: The War Begins*
The battles started subtly. First, a crazed **Grillby**, flames twisting wildly as he burned down his own bar. Then **Alphys**, who no longer recognized anything except the need to *eliminate threats*. Then **Undyne**, relentless and furious, her spear striking with unnatural precision.
Sans had never fought like this before—**not just for survival, but against people he once cared about.** Dodging wasn't enough. Sparing wasn't an option.
Every encounter chipped away at his patience, his humor, his calm. He was tired.
And then—**Asgore.**
Papyrus had begged him not to fight. The human had hesitated, trying to find another way. But **there was no "other way."** The king's SOUL had been shattered by the virus, and his raw magical power was unlike anything they had faced before.
Sans **had to go all out.** No tricks. No jokes. Just battle.
It would be his most brutal fight yet.
And if he lost—there'd be no Underground left to save.
---