"Blooky! Blooky, are you in there? Napstablook, for God's sake, say something!"

"Uh?" Napstablook let their headphones slide off and turned to face the door, which rattled in its frame from the force of the blows raining on it. Was that Alphys? They hadn't seen the scientist in ages, not since she'd shown up at Mettaton's door with plans for his new robotic body and had whisked him away… leaving them behind, despite all his cousin's promises otherwise…

They shoved that thought aside and drifted toward the door, opening it to admit the short, chunky lizard-monster who served as Asgore's royal scientist. Whatever was happening, it must be serious to drive the reclusive scientist out of her lab and to their door.

"Blooky!" She nearly tumbled headfirst into the shabby, single-room house before regaining her balance.

"Alphys? What are you doing here?"

"Oh, thank God, you're safe!" She threw her arms around them in a relieved hug, sobbing into the thin ectoplasm of their body. "You have to evacuate, there's a human loose in Waterfall and they're killing everything in their path!"

"Oh… but I'm a ghost, Alphys… without a corporeal body, I can't be killed."

"Oh." She blinked once or twice, as if that hadn't occurred to her before. "We'd still feel better if you were someplace safe. Just come with me, don't stop to grab anything on the way…"

"W-we?"

"Yes… Mettaton specifically asked that I take you back to the labs for safety."

"Mettaton? Oh, is he okay?"

"He is for now but… but Blooky… oh, I can't bring myself to say it!"

"Alphys, is Mettaton hurt?"

"No, but… oh, Blooky, he's gone to stop the human himself!"

Napstablook had never thought it was possible for a ghost to go cold, but their entire body seemed to flood with chill at that moment. Despite the broken promise, they still cared about Mettaton, watching his shows religiously and keeping updated on his ventures and exploits as much as they could. And while Mettaton repeatedly assured them that a physical body was everything he could have dreamed of and more, Napstablook had always feared that the inevitable would happen… that he would grow attached enough to his corporeal form to fuse to it permanently.

And if a ghost were fused to that corporeal form, they could be killed. And despite knowing that danger, Mettaton was deliberately putting himself in harm's way.

"Where is he?" Even Napstablook was startled at how dangerous their own voice sounded – no longer a soft murmur, but a harsh rasp.

"Uh… l-last I saw, he w-was heading for the Core. But Blooky-"

They didn't wait to hear her protest – they swooped out the door, leaving Alphys to sputter ineffectually in their wake. They hurtled down the tunnels of the Underground as fast as they could manage, not even bothering to dodge obstacles and simply phasing right through them. Perhaps a single ghost couldn't change the fate of the monster kingdom… but if nothing else, they should be able to talk some sense into Mettaton before the unthinkable happened. They could only hope it wasn't too late.

There were few things quite as heartbreakingly ugly as a fallen star… or as devastating as seeing the one who should have been a guardian angel brought down with a single blow.

The black-tiled corridor that connected the Core to the capitol, once the chosen arena for Mettaton to head off the murderous human, was spattered with oil and hydraulic fluids. Shards of metal and bits of broken machinery littered the floor, and the electric-burn smell of fried wiring filled the air. The faint whirr of a cooling fan, stuttering on and off, was almost drowned out by the steady trickle of fluid pouring out of a ruptured tank, marking a spreading pool of glossy black against the darker black of the floor.

In the center of the mess lay Mettaton, in his fiercely elegant NEO form… and nearly bisected by a savage strike across the midsection. As if that killing blow hadn't been brutal enough, further injuries marred the once-proud chassis – his wings were crumpled and slashed, his left optic was marred with cracks, and deep dents and scratches marked his paint from chest to boots. His foe hadn't been content with striking a mortal wound, but had beaten him with a bloodthirsty rage before moving on to the capitol.

It took only an instant for Napstablook to take all this in, but that instant felt like an eternity. They hovered a short distance from the leaking chassis, a tremor shaking their frame. What kind of creature could have done this… they had known most monsters were vulnerable to a human with enough killing intent, but this level of savagery seemed neither human nor monstrous, but something far more sinister…

A soft groan interrupted their thoughts, and they drifted to Mettaton's side. The mechanical idol of the Underground managed, with great effort, to lift his head enough to regard Napstablook with a flickering optic.

"B-Blooky?" His voice, normally as glossy and beautiful as the rest of him, was rough and shaky with pain.

"Mettaton!" Napstablook dipped low enough for the substance of their chassis to touch the floor, never minding the oil and other fluids staining the lower edges. "Oh Mettaton… oh no…"

"Blooky," Mettaton repeated, and a pained smile crossed his face. "S-sorry… you have to see me… like this…"

"Don't try to talk," Napstablook urged. "I'm going to call Alphys. If she hurries, maybe she can…"

A gentle touch to their lower body silenced them, and they looked down to see Mettaton's hand resting on them, leaving a smear of black against the eerie white.

"You care about me," Mettaton noted, his voice soft with pain and emotion. "It's… it's very nice… to see that you still care… that I haven't lost you entirely…"

"Don't talk like that!" Napstablook's own voice was stronger than they had ever managed before. "Just hold on! I'll get Alphys, she can fix you up!"

Mettaton chuckled, only for his laughter to dissolve in a fit of coughing as his fans snagged. "It's too late for that, Blooky."

"Don't talk like that!"

"Blooky…" Mettaton's optic dimmed, but he held his smile. "It's… it's okay… I bought her time… time to evacuate the Core…" Another coughing fit. "Perhaps it was foolish… to think I could stand up to a human… even with my upgrades… but… but if I could save one monster… perhaps it was worth it."

Napstablook's eyes burned, tears spilling down their face. "Mettaton… don't leave me… please… don't leave me again…"

Metal fingers tightened in the thin material of his body. "Don't forget me, Blooky… that's all I ask. Don't… don't let the Underground forget me…"

"Mettaton! Don't die on me! Don't, please!"

Too late. His grip relaxed, and his arm fell to his side as his optic finally flickered out. The stuttering whir of fans and hum of electricity fizzled out for good… replaced by the soft hiss of dust as his body disintegrated. His face was the last thing to go… and somehow, his smile remained until the very last moment, the final part of him to crumble away.

"No…"

Napstablook crumpled in a heap at the fallen mech's side, heedless of the oil and fluids soaking into their material. The corridor echoed with quiet sobs, the empty hallway amplifying the sounds until they almost muffled the soft pad of feet as someone slowly approached.

"No…" Alphys' hands flew to her mouth at the sight of the oil-soaked dust that was all that remained of the Underground's star. Her eyes brimmed with tears, but she steeled herself and dashed them away with a swipe of her claws before going to Napstablook's side. They twitched once as her hand settled on their back, but their sobs continued unabated.

"I'm sorry, Blooky," she murmured. "I'm so sorry…"

Napstablook curled up tighter.

"Blooky… we have to go. The human could come back at any time." She tried to pull them away, but they chose that moment to go insubstantial, and her hand passed through them. "Blooky please, there's nothing more we can do here."

The sobs stopped as suddenly as if she'd thrown a switch. For a moment she thought that perhaps she'd gotten through to them, and they would come to the labs with her… but their next words, spoken in icy tones, dashed that thought.

"No, Alphys… there's still something I can do."

Perhaps the human had walked this timeline before. Perhaps this wasn't their first time playing the destroying angel of the Underground, and they had expected a different figure to bar the way to the throne room. Or perhaps they simply found the sight of anyone daring to block their path disconcerting, given the trail of destruction and terror they had left in their wake.

At any rate, the human halted in their tracks in the middle of the grand hallway, frowning, weapon-arm hanging loosely at their side. By all accounts an unremarkable child, with shaggy brown hair and a striped shirt being their only real defining features, they might have looked innocent had it not been for the splashes of red that criss-crossed their face and torso, the death-dust that coated their clothes, the black oil that smeared their shoes. To one who didn't know better, there was no way this could be the terror of the Underground, the Destroying Angel of the prophecy.

The human frowned more deeply, lips parting slightly as if to ask why a ghost barred their way instead of a more substantial foe. But they said nothing.

"Expecting someone else?" Napstablook asked, bobbing gently up and down as if buoyed by invisible waves.

The human didn't reply.

"Nothing to say? Not even after you killed my cousin? I thought not." There was no hesitation this time, no self-depreciation – their voice was little more than an ethereal murmur, yet carried a great deal of steel and heat at the same time.

"You've taken the one thing I loved enough to fight for," they went on. "And maybe the rest of the Underground's scared enough of you to run and hide. But I'm not… because we both know you can't kill a ghost, right?"

Silence. Fingers tightened around the weapon.

"It's time for a rematch," Napstablook went on. "And this time I'm not lowering my HP to be polite. Someone has to stop you… and it looks like I'm the only one in the Underground who can." The eldritch glow of their body seemed to brighten, as if drawing strength from their own determination. "Take another step… and you're going to have a bad time."

The human raised an eyebrow.

"Yeah… you heard that line before, right?" A rare chuckle escaped them. "I had a good long talk with Sans before you got here. He told me things. Things about you. About determination." Their eyes flashed. "About the resets."

No answer. Human and ghost shared a long, silent gaze that nonetheless spoke volumes, each knowing what sort of stalemate they were locked in… and accepting it nonetheless.

Then the human drew a deep breath, and took one step forward.

"Go right ahead," Napstablook murmured. "You can fight me… but you'll never win. And if you reset… I'll be here. Every time. And you'll have no one to fight but me." They tensed, ready to dodge the first strike. "Forever."