Finn spends the next hour wandering through a maze.
It's eerie. The maze is made up of bits of dark land connected by equally dark bridges spawning large pools of water. The only light around comes from the water itself, which is glowing a faint turquoise, and from the silent blue flowers scattered around the bridges, neither of which provide enough illumination for Finn to see much more than their hand in front of their face and, occasionally, a new pile of white dust. The monsters here all turn out to be either creepy seahorses, fishtanks on legs, or Moldsmals like the ones Finn encountered in Toriel's domain, and Finn doesn't spend much time talking to them. They're too busy trying to get out of the maze, and they keep hitting dead ends.
Eventually, however, they cross the last bridge and make their way into a cave whose floor is studded with glowing gemstones, leaving the luminescent pools of water behind. There's another glowing plaque on the wall, which Finn eagerly approaches and reads out loud.
"The power to take their SOULs. This is the power that the humans feared."
Like we would've actually ever used it, the dummy grumbles.
"Wait." Finn looks at the plaque again, then down at the dummy. "Hold on. Was that what started the war?? The humans attacked the monsters because they were afraid that the monsters were going to take their SOULs?!?!"
History 101.
"But that... that... that's ridiculous!! You can't just attack a civilization and imprison it underground because you're afraid of a power that it might use against you someday."
Tell that to the Seven Sorcerors.
Finn is disgusted.
"That's evil!!"
Hmm.
Finn shakes their head and continues down the cave. The more time they spend down here, the more their respect for their own race declines. The monsters are very obviously the victims, still suffering from a wrong inflicted on them by the humans hundreds of years ago. They've been trapped in caves for generations, raising children who will never see the sky. Children who make wishes on rocks and hope and hope that they'll come true somehow. And as if that wasn't enough, now they're being wronged yet again, by a fallen human intent on finishing them all off for good.
Finn would do pretty much anything, at this point, to right those wrongs.
The cave empties out onto a narrow rock bridge traversing an expanse of dark blue water, and Finn makes their way rapidly across, their eyes fixed on the clump of white resting in the mouth of the cavern on the other side. It's a lot smaller than the other piles Finn's found in this area, and they soon find out why. The monster is the size of a fish bowl, and resembles a very pretty pale green cartoonish goldfish with a shock of droopy hair-like blue fins. Its face looks a bit like the face Finn carved on their jack-o-lantern last Halloween.
"Hi," Finn says, taking a cautious step back and hoping beyond hopes that this particular monster isn't a creep. It's far too cute and pretty to be one.
The monster blinks, looking up at them, then says in a very soft, quiet voice, "Hi." It seems to be trying to hide behind its droopy fins.
"I'm Finn," Finn tells it, relieved that it isn't saying anything weird. "What's your name?"
"S...Shyren," the monster replies, barely more than a murmur.
"That's a lovely name," says Finn brightly. Shyren reminds them a lot of the shy kids at their school, and they know that the best way to talk to them is to be as friendly and non-intruding as possible. As a pretty quiet kid themself, Finn is often mistaken for being shy, and they hate the way people generally treat shy children. "Your voice is so beautiful. It sounds like a waterfall."
"R... really?" Shyren peeks out from under her fins, eyes wide.
Finn nods. "Absolutely."
Shyren glances around, looking for all the world like she just remembered she'd died, then looks back at Finn, her eyes even wider. "W...who are you?"
"The savior of monsterkind," Finn says dramatically, and the dummy groans.
Shyren's eyes grow even bigger. At the rate they're going, they're going to take up her entire face.
"But never mind that," Finn says quickly. "Erm. You should probably find some place to hide."
Shyren lets out a terrified squeak and darts into the nearby water. The waves from the impact splash Finn in the face.
"I think I just traumatized her," Finn observes regretfully, wiping water from their mask with their sweater sleeve. "She's really nice. We could've been friends."
They continue into the cavern, which has two exits: one to the left, and one directly ahead. There's another glowing plaque on the wall, which Finn makes their way over to, and a gaping hole in the center of the floor, which Finn carefully avoids.
"The northern room hides a great treasure," they read. Their face lights up. "Ooooh!! A puzzle!!"
We don't have time to solve unnecessary puzzles.
"You're right," Finn sighs. They take a glance into the northern room, which they assume is the cave to the left. There's nothing in it except for a piano and another plaque on the wall.
We'll come back and solve it afterward, the dummy suggests.
Finn nods and starts down the path to the front. There's glowing plaques lining the wall, like the ones back on the deck where Finn first found out about the whole SOUL thing, and Finn slows down to read them as they pass.
"This power has no counter. Indeed, a human cannot take a monster's SOUL. When a monster dies, its SOUL disappears. And an incredible power would be needed to take the SOUL of a living monster.
There is only one exception. The SOUL of a special species of monster called a 'Boss Monster'."
Finn stops, staring at the plaque. "Boss Monsters?? Where are we?? Super Mario Odyssey???"
Just keep reading, the dummy sighs.
"A Boss Monster's SOUL is strong enough to persist after death, if only for a few moments. A human could absorb this SOUL. But this has never happened. And now it never will."
Finn rereads the plaque in their head before continuing down the path. Boss Monsters, huh? Why would a human want to take a monster SOUL, anyway? Weren't their SOULs already vastly superior?
They exit the cave hallway and emerge into yet another cavern, this one occupied by a rather forlorn-looking stone statue of an unidentifiable animal, only slightly taller than Finn. It's weathered down badly and cracked in places, but it appears to depict the animal sitting down, its head bowed. The statue itself is positioned in a small circle of dim light creeping down from somewhere far above, the only light source in the cave. Whatever hole is letting in the light is also letting in what appears to be rain, dripping down onto the statue's head one mournful droplet at a time.
The entire atmosphere of it is just incredibly sad.
"Hold on," Finn tells it, catching a glimpse of something useful in the next cave over. They move hurriedly into it, where they find, sure enough, a random old trashcan stuffed full of umbrellas. There's a wooden sign hammered into the ground next to it that reads "PLEASE TAKE ONE".
"Monsters are just very awesome and thoughtful creatures," Finn declares, obligingly taking an umbrella. They take the blue one, because blue is their favorite color. "You'd never find something like this on the Surface. You'd have to pay at least five dollars."
That's sad.
"No, it's not," Finn replies. "It's human nature."
They return to the statue and carefully wedge the umbrella into the statue's arms so that it covers the statue's head and protects it from the rain.
"There," Finn says, enjoying the familiar sound of the water tapping on the umbrella.
And the sound of something else...
Finn holds their breath as a haunting tune echoes out of the statue, riding quietly out into the underground air and ringing against the stalactites. The stern silence dissipates, laid waste by the vibrations of what sounds like some kind of music box, hidden inside the statue. The song is soft, not mournful or scary, but not cheerful, either... it tells the story of loss, but not really the loss itself: the memories of something happy, something that's gone forever.
Listening to it, Finn is reminded sharply of their dad. Of how things used to be, before everything happened. Like, they know what happened, and where they are now, but they can concentrate on the happy memories as well, blending the two, dulling the pain. Whoever chose this music... they really understood what it means to have your world turned upside down. To have no choice but to accept what happened and move on, treasuring the things you can only remember.
It's the saddest and most beautiful thing they've ever heard.
Finn, says the dummy urgently, breaking the spell. There's someone coming.
Disgruntled, Finn turns.
There's a bright yellow monster barreling towards them.