A/N: My apologies for taking so long. My muse had been elsewhere. I also accidentally deleted the first draft to this chapter. And then my cat deleted a good chunk of it halfway through.
Waterfall. An interconnected network of caves and tunnels where all sound is muted under the roar of water tumultuously cascading from the surface into an unexplored abyss beyond the depths of the Underground. In lower areas, piles of garbage accumulate, carried by the water down from what is presumably a dump on the surface.
As it was the only source of goods, information, or really anything at all from the surface, the area was a popular spot for monsters to salvage materials.
Batman walked quietly, footsteps making no sound against the stone floor.
There were monsters, of course. Swimming in the water, digging in the trash, washing the walls for reasons unknown...
Echo flowers murmured their repetitions constantly. An echo flower would capture a sound, then repeat it, and a different echo flower would catch the sound and repeat it back. There were places where the blue flowers were alone, left to repeat to themselves until it caught another sound. Batman didn't care to listen.
He had to keep moving forward.
Spurred on by something calmer than urgency and steadier than anticipation, he continued. The path wound through and around pools and rivers, stone walls and eroded clifflike banks making it impossible to see too far ahead or behind. He remained vigilant, and strode on undaunted.
Then, without warning, out of absolutely nowhere, a Temmie appeared. Small. Both dog-eared and cat-eared. Covered in white fur.
"hOI!" The monster was vibrating incessantly. "Oi'm temmie! Issa..?¿? BATZHOOMIN! So cyoots!"
Batman examined the four-eared creature, which stretched out a briefly elongating leg towards him, touched him, then... Rolled away into nowhere as if nothing had occurred.
To say that Batman did not know how to react was an understatement. To say that he was thoroughly baffled and absolutely incredulous was only somewhat less of an understatement. Following Temmie was impossible, and likely not a good idea even if he could. He wondered why it had done that. Was it sent to observe him? Confound him? Or was it just a very, very strange creature? Either way, he didn't let his guard down.
This proved to be the correct course of action when, not ten minutes later, a glowing blue spear whizzed towards him.
He leaned to the side, and the attack missed him entirely.
Two more shots passed as he turned to face his assailant. There was nobody there. More spears appeared out of thin air, and he leapt out of the way. He heard a faint clinking, the sound of metal on metal, and glanced towards it.
Just an echo flower.
He'd already had a plan to determine the line of sight of his attacker(s), get out of it, and safely subdue them.
It was a good plan. It was crafted by years of experience in attacking and being attacked in the dark. It accounted for not being able to rely on his sense of hearing, due to the echoing of the blue flowers. A practical plan, useful in many situations against humans and metahumans both. It made few assumptions and proved effective in many situations. Batman was experienced and skilled when it came to combat, self-defense especially.
It also completely failed to work as his legs refused to respond. He looked down to see what impeded him.
His soul had been revealed, turned green from some sort of magic. All else was black and white.
The clanking of someone in armor marching towards him came from all directions.
"Seven."
And thus appeared Undyne. She stepped into view before him.
"Seven human souls and King ASGORE will become a god."
So the armored monster was monologuing. He would listen to what she had to say. So the Asgore he was warned of gained power from human souls. Was this monster king responsible for bringing Batman here?
"Six. That's how many we've collected thus far. Understand?"
She didn't wait for an answer. This speech was clearly rehearsed.
"Through your seventh and final soul, this world will be transformed."
He could interrupt the monologue at any time, but that would yield him no information and be rude besides.
"First, however, as it is customary for those who make it this far... I shall tell you the tragic tale of our people."
If she wanted him to know all this before she killed him, what would she have intended to do if she hit him with that earlier barrage? Perhaps they were nonlethal magical blue spears, as unlikely as that seemed.
She continued speaking.
"It all started, long ago..."
She paused, presumably for effect.
Undyne was in full platemail of thick iron, helm obscuring her face except for her right eye, which was just barely visible. Batman could tell her left eye was covered, possibly patched over due to a wound. The visor and jaw of her helm were fashioned to resemble a maw of jagged teeth, and a plume of red hair sprouted from the back.
The steely visage of her helm stared blankly at him in the darkness.
It seems she forgot her line.
"Long ago?" Batman prompted.
Undyne regained her verbal bearings.
"The war. The war between your kind and ours. Humans and monsters. Humans feared us and drove us to near-extinction and trapped us in this underground tomb. No matter where we dig, how far we swim, or how high we fly, we cannot escape. We are trapped. Sealed in here by YOUR kind. Sealed in here by the Barrier."
She manifested and brandished a spear, pointing it at his now-green soul.
He'd never heard of the war or the Barrier, or even monsterkind in general. Could this be an alternate universe? Or was this place like Gorilla City, hidden where none would know about it? If this was still the same universe, it would mean all accounts of the war were wiped from history. ...It sounded plausible either way.
"There is only one way to destroy it. Seven human souls. Humans can enter, but we cannot leave. When we have all seven, Asgore will destroy the barrier. You are the seventh. The last soul. The only one standing in the way of everyone's hopes and dreams! Between us and freedom! Between us and sunlight!"
She lunged, and a blue spear manifested in Batman's hands. Seems she wanted to give him a fighting chance, even with her magical entrapment. He parried easily.
Spears manifested in the air and shot at him, while Undyne herself attacked with the spear she held. She was quite fast, considering the fact she was in full armor. This green magic she'd cast on him gave her a significant advantage.
She spoke while she fought for some reason.
"Most monsters don't realize you're human. But I know my history! I know all about your cool outfits, your beautiful swordswomen, and your giant robots! You can't get past me!"
He didn't dare release the spear. This was magic, after all. There was no guarantee that his body armor or the branch he picked up earlier would do anything to impede the projectiles flying at him or the matching spear in his opponent's hand. Any attack could be potentially lethal.
No offense to Zatanna, Dr. Fate, or any of the others who used magic, but Batman hated dealing with magic. Its volatile, unpredictable, physics-defying nature always made everything more complicated and uncontrollable.
"You're good. This is going to be a challenge." Her projectiles increased in speed and number. He continued blocking her attacks, but knew he shouldn't let the fight continue for too long. This was already tiring, and he wasn't keen on being impaled. She was aiming straight of his soul after all. He couldn't expect to survive even a single hit.
Undyne was relentless.
"What are you humans made of? Anyone else would be dead by now!" She exclaimed, swinging the spear she held in a sharp thrust. Batman batted it aside, straining against the monster's strength.
It shouldn't have been difficult to subdue her peacefully. Account for the armor. Hit firmly, without causing much permanent damage. Use the branch instead of the spear in order to eliminate the unpredictable factor of magic. Knock her out. Get her to stop attacking. To stop binding him there. Make this stop.
She didn't stop attacking. She sent volley after volley as they fought, Batman straining and twisting as well as he could to land blows, to subdue her. He couldn't go for her legs and trip her while magically locked in place.
"Hah, you hit hard. But not hard enough! Don't think I'll make the mistake of letting you go! Just give up already and die!"
And such they continued.
He fought in silence as she refused to stop, insisting on his death. She continued to pour her anger out onto him, her hatred for humans.
But he found an opening. And he took it. A clean strike to the head. She'd probably be left with a concussion. But she would stop. And he needed her to stop.
She should have been safely knocked unconscious. Her magic should have released him. She should be fine, only to wake up some time later with little more than a concussion.
She wasn't.
She stopped but didn't fall over.
"Nghaah..." She was panting. "You're stronger than I expected... But I... I can't let it end here! For Alphys, Asgore, Papyrus... For everyone trapped here... I must endure! Everyone's counting on me to protect them! Everyone's counting on me to free them! I can't stop now!"
Her form began to waver. Her feet were fading. Batman didn't know what was happening.
She sent a frantic flurry of spears his way, which he parried with her own. He tried to move. His soul was still green and his legs still would not move. He watched in horror as she began quite literally falling apart, her feet and legs turning to dust before his eyes, swirling around desperately beneath her torso.
She didn't seem to notice.
"Come on, is that all you've got!? Pathetic! You're gonna have to try harder than that!"
He didn't. He parried a weaker flurry of spears, still rooted in place. The disintegration crept up her legs, taking her armor with it.
He tried to reason with her. "You don't have to keep doing this... You're dying." Maybe this could be reversed? If she rested, if she calmed down... What was happening to her?
She didn't listen.
She fired another barrage, a few spears weakly whizzing by.
"Dying? Don't kid yourself! This... This is just a flesh wound! You haven't defeated me, human! S-see how strong we are when we believe in ourselves?"
Her next attack didn't even make it to him.
"Heh... Had enough yet?" She continued to ignore her fading limbs and body, her spear long disappeared.
A few more spears floated weakly in the air.
"I won't... give up..."
The spears themselves wavered, flickering out of existence. Even the spear he held disappeared.
Her body was little more than a cloud of dust holding a vaguely humanoid shape.
"Ha... ha... A-Alphys... This is what I was afraid of... This is... This is why I never told you."
The dust that composed her body lost its shape.
But he still could not move. Her magic continued to cling to him, not releasing its grip even in this state.
"No... no!" A voice rose from the cloud. "Not yet!"
The dust tried to coalesce itself. It swirled madly, driven by some unknown and likely magical force.
"NGAHHHH!"
She reformed.
And Batman made the mistake of letting himself believe, just for a moment, that he hadn't killed her.
"I won't die!"
Something was wrong.
"I WON'T DIE!"
She was melting. Her voice began to slur.
"I... WON'T... DIE!"
Her arms were dripping on the floor. Her legs were a single puddle on the ground. Her face had melted and contorted into a misshapen lump.
"I! WON'T...!"
And like that, she was gone. Dust in the wind.
He was freed, but did not move.