The World, Upside Down

by Last Haven

Frisk wakes up to find that something has gone terribly wrong-they are back in the Underground and monsters are trapped again, but Frisk didn't reset. They are still a grown adult. Flowey's being helpful. Monsters are not sweet but strange creatures-now they're dangerous. Frisk sets out once more, to return home and fix whatever ails this world. Frisk in Underfell

6. Stand Your Ground

Frisk dreamed of a field of yellow flowers. At first, the flowers were only as tall as their ankles, but as far as their eye could see, it was nothing but a sea of yellow. The sun beat down upon them, relentless, searing—they needed to find shade or they'd be burnt to a crisp. They tried to move, but their feet caught on the stems and leaves of the blossoms, the roots tangling around their ankles. They didn't feel dirt or mud beneath their bare toes, just mores plants. Gritting their teeth, they tried to force their way through the plants, but their legs only seemed to sink deeper each time they fought their way forward.

They barely got three feet before they realized that the plants were now tangled up around their knees. They had to reach down and yank on the plants like handholds to keep moving, but then the plants were up around their thighs and they're practically wading through them.

That old familiar feel of drowning kicked in as the plants crept up their hips, up to their belly. They could feel their chest fail to expand as far as it had the breath before, again and again until they could only manage a few shallow breaths. Frisk's eyes rolled in their head as they searched for something—anything—to grab onto. That was when their throat began to tickle. They coughed, but it persisted until suddenly they felt bile burning their throat. They opened their mouth, but only a gush of golden flowers fell from their lips. Frisk tried to cry out, but they choked on their vomit of buttercups. They're coming from inside me—the buttercups are inside me already.

With a gasp, Frisk sat up. The world spun at the abrupt change in position, but thankfully settled down fast. Looking around, Frisk remembered where they were. Taking a breath, Frisk shoved their sweaty bangs out of their face and shivered.

*You wake from your horrible nightmare only to find yourself in another.

"It's not that bad," they muttered, sighing. "Well, I mean, I've probably had worse."

*You do not believe your own lie.

"Okay, kiddo, no more sass unless I get a cup of coffee, okay?"

They waited a moment, but there was no response. Well, at least I'm not getting heckled first thing after I woke up. They glanced around and found Flowey still asleep. Getting up, they groaned and stretched, joints crackling. As surprisingly comfortable as sleeping in a bed of flowers was, it didn't stop Frisk from feeling sore all over later. Maybe the flowers had prompted their horrible dream? It made as much sense as anything else did. They grabbed their pants and checked their pockets before sighing. The monster candy had been soaked through and ruined during their dip in the water. There was nothing that could be done except wash out the bag and keep it in hopes that they'd soon find new restorative items. Their cigarettes were ruined too, but the lighter at least worked fine. Reluctantly, they tossed the ruined pack into the water—they didn't like to litter, but well, it was a literal dump. Most of the rest of their stuff was okay, not that there was much to have.

They pulled their clothes on, hesitating for a moment as they looked at their binder before storing that too into pocket. I wish I could get my dimensional box on my phone to work. I'll have to talk to Alphys about it when I get home. It hadn't worked since they woken up in the Ruins, but maybe it just had something to do with the fact that they weren't in the right world in the first place. Whatever, that was something for Alphys or Sans to ponder over after they got back home.

Sitting down next to Flowey, they gave him a nudge before pulling their socks and boots on. They were just going to have to deal with wet feet today—they weren't going to chance cutting their foot open on some trash as they waded through the dump. "Wakey, wakey, bud. I think we've lingered here long enough."

The flower yawned as his petals unfurled, like he was stretching his limbs. He shook his head a few times before blinking sleep from his eyes. "What time is it?"

Frisk paused to check their phone. "Hmm. About three hours since we were on those bridges? We had ourselves quite a nap."

Flowey straightened bolt upright. "Are you kidding me? Frisk! What if we missed our chance to get past Undyne?"

"Well, we will just have to cross that bridge when we come to it," they shrugged before turning back to him with a sly grin. "Although considering my luck with bridges lately, we should probably be careful about it."

The poor flower twitched as he glared at them, like he was actually disgusted. "Seriously? You almost died a few hours ago and now you're cracking jokes about it?"

They beamed at him. "What better way to get over trauma than to make light of it?"

"Frisk!"

"Ease up, buttercup." They gave their laces a hearty pull before tying them into a bow. Satisfied that it would hold up, they climbed up to their feet and crouched down to offer Flowey their hand. "Look, qué será, será, okay? We'll deal with it as it happens."

He grimaced, but climbed up into their hand. "Don't you think that's a little too casual?"

"Possibly," they conceded as they lifted him up and then offered him the shirt strap he'd been clinging to for the last two days. "But, again, there's not a lot I can do about it besides keep going forward. Speaking of, let's get moving."

With a sigh, he nodded.

They marched to the water. It rose up to their ankles, but thankfully the water spread out so much here that it wasn't any deeper than that. Frisk shuddered as they remembered their dream, but kept their chin up.

*Pushing on, despite your fears, fills you with DETERMINATION.

Thanks for the update, kiddo, they thought wryly as they weaved around a heaping pile of trash. They paused to let a cardboard box float past them before moving on.

"Uh, before we go much farther, I think there's something I should tell you about," Flowey said as they walked further into the piles of trash.

"What's up?" They paused at a familiar cooler, but peeking inside revealed nothing but a funky odor. Disappointed, they shut it and kept moving.

"Yesterday, when Papyrus pulled you from the water, your soul… did something weird."

Frisk stopped dead in the water to look up at him. "What?"

He frowned and shifted about. "It… when Papyrus pulled you out, he started pushing on your chest. CPR, I think."

"Fair enough." Funny, their chest hadn't hurt once they regained consciousness.

"You know how your soul usually pops out whole from your chest during a fight?"

Frisk nodded; it'd been incredibly disconcerting at first, but they'd gotten over it pretty quickly.

"Well, instead of popping out of you and floating up, it was already out—but it was, like, broken into pieces and it quickly came back together. When it did, you started breathing again. Do you know what it could mean?"

It took everything they had not to let their body shiver from head to toe. As a matter of fact, it did sound familiar, but it would be pretty awkward to admit how they knew—during their final battle with Asriel, their soul had refused to die by re-fusing each time it shattered. Distantly, they noted that each time they had nearly died and refused, their health had returned as well. Well, that explains why nothing hurt. Still, had been a one time thing, or at least, they assumed it had been. They'd been damn careful in the time since then to not get killed, lest they risk a reset.

Well. This was weird, but not unpleasant news. Nonsensical—they'd never been more determined in their life than during that fight, if they were honest with themselves—but then, this world often seemed to be. So, either it was pure luck, or they might have accidentally stumbled into a strange sort of immortality. That in and of itself was kinda terrifying, but it would work for them for now. They could worry about it later. Or, maybe it really was just a fluke—they hoped so.

"I… think it means death might have a little harder time claiming me than most."

Flowey grimaced. "What does that mean?"

"Well, I'd guess it means my soul re-fused. I, uh, can only take your word for what you saw, but when my determination is high enough, my soul will refuse to shatter. So, I can, on the rare occasion, be really hard to kill off."

"…are you pulling my roots?"

"No. Look, take my word for it. It's probably a good thing."

He looked suspicious, but didn't argue. "Well, you better not try to use this as a reason to get sloppy and take even more risks."

They had to chuckle. "Look, Flowey, I have no more urge than you to test it out. Hell, it may have just been dumb luck, and in that case, I really shouldn't try it out. Now, let's get back to moving, alright?"

"Fine by me," he said, his voice loud. They chuckled as they started wading through the dump again, walking around piles of junk. "This place weirds me out. There's too much junk and it's all so strange. I mean, look at that dummy! That stupid thing is creepy."

Shaking their head, Frisk walked past the dummy but frowned. Wait, a dummy? Why did that sound-?

Behind them, they heard a growl. Freezing, they turned back just in time to see the dummy's lopsided head start to twist about. Once it turned about, a pair of furious looking eyes opened. Flowey mumbled a shocked curse, but the dummy vanished under the water.

Knowing what was coming, Frisk wheeled around in time to see the dummy pop out of the water. "YOU FOOL!" it roared. "I'm not any old dummy—I'm a ghost that lives in this dummy!"

"Oh my god," Flowey murmured, ducking behind their shoulder. "I know you don't like the word, but that thing looks even crazier than Toriel."

Frisk shot him a look, but they didn't want to argue right then. There were more important things to worry about.

Not that Chara seemed to get that note.

*Why anyone would want to live in a dummy is beyond you.

Well, admittedly, that's true, but I try not to judge people over it, Chara.

*The point stands.

"A ghost that lives in a dummy isn't creepy or stupid! Plenty of ghost chose to live like this. Many of my cousins chose corporal forms." The dummy paused and glared at Frisk. "Wait, you are—you're a human!"

Instinctually, Frisk took a step back, but they knew it was useless already—it was hard enough wading through the water logged trash, running in it would be impossible. "So what if I am?"

"A-a human! Here, in the Underground?" It paused and cackled for a moment. "This, this is perfect! I can hand you over to the Overlord—I will be justly rewarded. I will be given a new, glorious body. I will fight by the Overlord's side! I will live out the rest of my days, beautiful, pampered, admired! My cousins will live like princes, my cousins-" Abruptly he stopped. "My cousin… I had a cousin who lived in a dummy in the Ruins…"

"Oh shit," Flowey muttered, hiding even lower down Frisk's shoulder.

"Someone—someone came and attacked my cousin in the Ruins." The dummy scowled at them. "Was it you? Did you try to murder my cousin?"

"No, of course not! The caretaker of the Ruins, she—I'm human anyway, I couldn't hurt a ghost-"

"SILENCE!" It's body began to burn red with rage. "Despicable. Despicable! DESPICABLE! You, you awful bastard! You try to murder my family, hurt their neighbors, and then lie to my face! You—you! I have never been madder in my entire life!"

"Oh, hell," Frisk mumbled, trying to crouch down into a defensive position. The dummy was shaking before them, bobbing back in forth as it growled and roared in rage. Whether they were prepared for it or not, it looked like it was going to come down to a fight. "Flowey, I might have to toss you to shore if things look bad."

"Don't you dare toss me again!" he hissed.

It roared louder. "Horrible creature! Oooh! If I had hands, I'd strangle you. If I had teeth, I'd bite you. Oh, if I had—guuuooo! I'll kill you, I swear! I'll kill you, I'll kill you, I'LL KILL-"

Frisk could only stare in horror as the dummy suddenly began to burn in a bright white light. Soon, the form vanished in the light that began to burn as bright as the sun. Frisk had to turn their head away as the light overwhelmed their sight.

Then, as suddenly as it happened, the light vanished. Spots danced in their vision, but when they turned around, the dummy was still floating before them. The anger had vanished from its face and now it bobbed around with a stunned look. Slowly, a smiled spread across its face. "This… this is-! Eureka. Eureka! EUREKA! Human, human, look! Haha, I don't believe it! Look at me, human. Do you see? All that anger you gave me, it finally did it! My soul has fused with this body! I'm finally completely corporeal!"

Frisk and Flowey paused before sharing a long look of utter confusion. "Con… congratulations?" they offered.

The dummy burst out laughing and began to sway through the air. "Oh, human, how wonderful it feels! My lifelong dream realized and it's all thanks to you, human! Even if you are an unforgivable jerk and your pet's an idiot, I can't thank you enough. I'll skip destroying you for today."

"Hey, I'm no one's pet," Flowey grumbled, finally lifting his head up over Frisk's shoulder, although he was ready to duck back behind them at the first sign of trouble. "At least don't insult me while you thanks us, you jerk."

"Hush, Flowey," they murmured, straightening. "Well wishes to you, uh, dummy, on your new body. Thanks for, uh, not killing me?"

The dummy started to cackle, not mean spiritedly but excitedly, spinning through the air in its glee. It didn't seem to care one iota how loud it was being.

Which explains why another ghost came barreling down the path, screaming. "Will you just shut up already?!" Napstablook howled. When he looked around, however, he paused to stare confusedly at his cousin and then Frisk who helplessly waved at him. "You again?"

"Blookie!" The Glad Dummy cheered, twirling about as they flew closer. "Look at me, cousin, look! I'm really corporeal now! The human got me so mad, I fused. Oh, isn't it wonderful. Wonderful? WONDERFUL?!" It laughed again. "Oh, I'm so gotta go show this off—wait until everyone sees me! Later, cousin." With one last laugh and a twirl, the dummy flew away, leaving only a very confused trio.

Napstablook watched their cousin go, looking utterly baffled before turning to look at Frisk again. "Uh… thanks? I think? For them, at least? Uh, whatever, I—I'm going back home. Later."

Frisk watched as the ghost vanished before turning their head to look at Flowey. "Do you know what's going on? Because I'm still kinda confused here."

"Nonsensical," Flowey said sagely after he corralled his wits back into place. "This place is completely nonsensical."

Well, he wasn't wrong. "Good to hear that you're making some good use out of that word."

"Yeah, yeah, whatever. Now, let's get out of here quick before either one of them change their mind and try to come back."

Nodding, Frisk waded their way out of the water and headed north. They paused at the crossroads, looking around. Heading west would only send them back the way they came. East was the way to Hotland. North, however, would lead them to Undyne's house if they went one way, or to the snail farm if they tried another. Frisk considered their options and headed north anyway, mostly out of curiosity.

What they found, needless to say, surprised them. On one hand, Napstablook's house was surprisingly the same. On the other hand, the neighboring house was a charred husk.

"Whoa," Flowey muttered, craning his head over their shoulder to get a better look. "This wasn't like this last time I was here."

"I thought you didn't come to Waterfall often?" Frisk asked numbly as they walked forward to get a better look at the wreckage. It really was a lost cause—the floors were black and warped, the foundation visible through the hole in the middle of the floor. They frowned at the walls. What was on there? They walked to the side to get a better look.

"Not if I could help it. Still, this place is usually quiet—no one usually visits around here, so it's easier to hide." He shuddered. "The only thing is, Undyne's house is just around the corner. So let's not linger here, if you get what I mean?"

Frisk dug their phone out of their pocket and used it as a flashlight. "Okay, okay, just give me a second. I just want to see what this says… oh."

GOOD RIDDANCE YOU FREAK

LOSER

WHO NEEDS IDIOTS LIKE YOU

There was graffiti spray painted all over the inside of the building. Curses and insults scrawled up and down the walls, onto the floor, and whatever little furniture remained. Stepping back, Frisk grimaced, knowing in their gut who'd defaced the shell of a house. "Napstablook has some real anger issues."

"Oh, now you see that?" Flowey drawled.

Frisk took a step back, looking over to Napstablook's house. Without its neighbor there beside it, it felt oddly lonely. Sorry, Blookie. This world's version of you has too many problems for me to help with in one day. Maybe, after all this is over, someone else will be able to help him. As for me, I got a schedule to keep. Nodding reluctantly, Frisk turned and came back they way they came before heading west.

"Oh, hey!" Flowey said, perking up. "Go north here! The old turtle might be a snob, but at least he doesn't overcharge."

Frisk blinked up at him. "Really? Thank god. I'm all out of candy."

"Just, uh, don't be rude to him. He still knows how to throw that hammer and he's got good accuracy," he added before shuddering.

Frisk ducked their head through the doorway and smiled at the familiar scenery of the shop. They'd popped into Gerson's shop a few times during their own trips through the Underground. They'd loved the way the pretty crystals in the walls sparkled and threw rainbows of light from the lamps next to Gerson. The old turtle himself was leaning back in a chair, his feet propped up on the counter. He still wore his archeologist outfit and hat—the brim was missing a chunk. When he looked up, they were unnerved to see that the missing chunk lined up with the missing eye under the brim. "Customers, eh? Well, come in. I got some junk for sale. Just don't try anything funny, human. Yeah, I know what you are."

Frisk raised their eyebrows as they stepped in. "You know what I am and yet you let me in anyway? How kind of you."

He scoffed. "Hardly. Your reputation precedes you, human. You got monsters all up in a tizzy." He shook his head. "A human sparing monsters. You must be as crazy as me."

Flowey poked their cheek with a leaf. "Told you."

"Ha ha. Well then, can I see the, uh, wares then?"

Gerson gestured to a box of stuff next to him. "Knock yourself out."

They knelt and dug through the items. To their confusion, all that was in there was healing items—they distinctly remember some items from the fallen humans being in there during their own runs. Where were they now? Had they been lost when the human had died, tossed aside into Waterfall's waters? Or had someone come through and bought them? If they had, then why? Shrugging, Frisk counted their money and decided to buy some sea teas—the crab apples healed more, but the small bottles of sea tea wouldn't take up too much room in their pockets. While they were digging around, their face lit up as they discovered a half crushed pack of cigarettes. They pulled it out and examined it—the plastic around it looked fine and intact. Feeling it with their fingers, they knew a few of the sticks had been ruined, but there had to be at least a few good ones left.

They held it up to the turtle. "How muck for the smokes?"

Gerson eyed it lazily before shrugging. "15 gold. That's my only offer."

"Fair enough. I'll take it and these sea teas."

Gerson held his hand out; obediently, they dropped their money into his palm. Once he nodded, they began to stuff their items into their pockets wherever they found space. Watching them put their items away, Gerson chuckled and leaned further back into his seat. "Funny that I get less trouble out of humans than I do any monster patrons."

They glanced up at him. "Get many humans passing through here?"

"Occasionally. They don't always drop in and they don't always make it this far, but when they do, they seem all too happy to get out of my way without much prompting."

Flowey poked them in the back of their head. "Frisk, let's get going."

Frowning, Frisk nodded to Gerson. "Thanks for the stuff, sir."

The old turtle waved them away. "Pfft. That's the first time I've been thanked in awhile. Humans. Bah. Git going now, go on."

Frisk left and started heading east again. Moving through the dark rooms with light up mushrooms, glowing crystals, and more waterfalls, they encountered a few monsters along the way, including an Aaron who they scared off by making spooky noises at him. Frisk only paused once to consider the hidden path to Temmie Village.

"Should we go visit the Tems? They might have some cheap items."

"Uh, no."

"Oh, come on. Don't Temmies like humans?"

"Yeah, they like humans alright—they like to eat them." Flowey scoffed. "Once the Overlord's Enforcers had to come out here to get a human who'd gotten lost in the dark rooms and got caught by the Tems. They had to slaughter half the village, and even then, all that they managed to recover was the soul."

Horrified, Frisk hurried through the maze and the one after that. They paused at the dark room, flinching when they stepped into the ankle deep water at first. They wandered to the far side of the room and noticed, with no small amount of dread, an echo flower. Walking over to, they waited by its side for it to talk to them.

"Yo!"

Frisk blinked. That wasn't what they were expecting.

"U-um. Yo?"

*The sound is coming from behind you.

Oh. Um. I knew that. Turning around, they brightened when they saw Monster Kid behind them. "Hey, it's you! You're alright, too?"

The child blushed. "Y-yeah, I'm alright. I, uh, I was too fast for them to get me!"

Frisk grinned. "I see. That's fantastic. I was worried about you."

"What, me?" He blinked up at them before grinning back. "Nah, no way. I was totally too slick for them. But uh, you're the one they were chasing." He paused, frowning. "Are-are you okay?"

They resisted the urge to giggle in delight. "Did I worry you? Sorry. I got lucky though, so I'm fine."

"Lucky? You're so much better than lucky!" he nearly shouted, bouncing closer to them. When he looked up at them, his eyes were shining. "You were so cool! You ran so fast and-and you never even cried when you got stabbed-" Frisk clenched their hand. "You actually got away from Undyne! That's, like, the most badass thing ever!"

Frisk found themselves smiling softly. "You're sweet. I'm not nearly as cool as you think I am—but you're kind to think so."

"No way, you totally are! Even if you're…" He paused and shifted uncomfortably.

Frisk had a feeling they knew what he was about to say.

"Even if… hey… Are—are you really? A human?" he asked, gazing up at them. He looked like he was torn between fear and hope—but fearful or hopeful of what? They had no idea what he wanted them to say, but looking at him, they decided to try the truth.

They nodded their head. "I am. Sorry for not telling you earlier."

"O-oh, um. It's okay! It's just, um," he paused and scuffed his claws against the ground. "I'm such a turd. I said all that stuff about watching Undyne kill the last human and, um. Yeah."

"Well, it's not like you're the first of your kind to say as much to my face," they said, reaching out to pat the top of his head. "And most of those monsters said it cheerfully, knowing exactly what I was! Don't worry, I won't hold it against you."

He blinked up at them, mouth agape. "R-really?"

"Hun, I've heard a lot worse things said about me before. I'll live."

He looked up at them silently for a moment. Then he beamed up at them. "Wow, you're so cool! You're nice and you're fast and smart! You're soooo much better than Undyne—she nearly speared me to death! Which, admittedly, would be kind of an awesome way to go, but you're so much cooler than she ever was!"

Frisk blinked before scratching the back of their head. Lord, they hadn't had flattery laid on this thick since that time the French ambassador's daughter got a massive crush on them and tried her best to woo Frisk. Of course, they'd been about four years older than the girl and hardly spoke a word of French. It took two hours to convince her that they weren't ready for a relationship, let alone one with a thirteen year old although they worded it kinder than that, and they'd had to put up with Alphys giggling at them the whole night. God, they were almost dead certain she still had the fanfics she wrote about them saved on her computer somewhere, just waiting to be brought out to tease them.

Flowey didn't seem to amused either. He grunted in disgust and prodded the back of their head with a leaf. "Frisk, send him away—we can't stop moving now."

He had a point. Frisk cleared their throat. "You know, you really are sweet." He paused and fidgeted in delight; they took it as their cue to press on. "And I'm really am glad to see you're alright. But Undyne, you know, she's still looking for me. I don't think it's safe for you to be seen talking to me."

He drooped, tail curling around his feet as he nodded. "Yeah, I—I figured. I just, I just wanted to tell you though, how cool I think you are." He paused and brightened. "Hey, if you're ever in Snowdin again, you should totally come to our school! Everyone will totally think you're the best. I'll be the most envied kid in school once they hear that I met you!"

They smiled softly. "So, you're planning to go back home?"

"Heh, yeah." He shrugged and looked away. "I figured that Undyne will probably try to spear me if she sees me again, so I'd better wait for awhile before trying to sign up for the Overlord's troops. That and I'm getting kind of hungry. My mom's probably got dinner waiting for me at home."

"Sounds good. Get home safe, okay?"

He nodded and smiled at them. "Okay. See you later, human."

"The name's Frisk," they laughed.

"Frisk then! See ya!" he shouted over his shoulder. They waved goodbye as he ran off—he didn't get far before he planted his face in the ground. A moment later, though, and he was up and running off into the shadows.

They watched him leave with a fond smile, shaking their head.

"Thank god," Flowey groaned, resting his leaves on their shoulder like he'd climbed up there. "Maybe now we can get around without having to worry about Undyne hearing you two yapping all the time."

Frisk chuckled and patted his head. "Aw, don't be such a grump. He's just a kid."

"A dumb kid," he huffed. "Come on, let's get going already."

"Okay, okay, no need to be mean," they said as they looked around for the proper passage. They brightened when they saw the path that they had missed in the shadows. They hurried past the echo flowers and their grim conversations, resisting the urge to clap their hands to their ears to block it out, but afraid that if they did they might miss something important.

They moved so quickly to escape the haunting words, that they nearly tripped hurrying out of the corridor. Catching themselves, they straightened and froze.

"Wow," Flowey breathed after a moment. "This, uh. This is new."

It was another corridor, but it hardly matched the surroundings at all. If Frisk was perfectly frank, it looked like it belonged to the western side of Waterfall—not nearly all the way to the east. Hadn't the bridge where Monster Kid had first fallen been here? And yet, it was nothing more than a plain corridor. Suspicious, Frisk walked further into the corridor, pausing at the only landmark in the corridor.

The grey door stood out sharply, looking as out of place as a Great Dane in a line of Pomeranians. It was placed perfectly in the middle of the wall, like it had grown out of it, like it had always been there.

Staring at it made Frisk's head hurt, as if they were looking into the sun. They gazed at it from the corner of their eye and still it hurt. Unbidden, their hand reached for the knob.

"Frisk," Flowey murmured into their ear. "I don't think this is a good idea."

In their gut, they agreed. And yet, their hand kept moving. Slowly, it neared the knob; their stomach flipped with anticipation. Once their hand touched the knob, their palm throbbed and Frisk drew it back with a hiss.

"Frisk! You okay?"

Biting their lip, Frisk rubbed the palm of their hand, they thumb tracing the stitch they sewed in hours before. The spell the door had cast on them was over now, at least, and they found themselves repulsed by it. "Let's get out of here," they whispered, taking a cautious step to the side.

"Don't need to tell me twice."

Turning, they hurried forward and didn't dare look back until they found themselves at the edge of another bridge. Pausing, they thought about glancing over their shoulder but stopped themselves at the last moment. Whatever devils lay behind them, they could stay there—Frisk wouldn't invite them forward. Lifting their chin, they took a deep breath and continued eastward.

Walking forward, however, they found themselves abruptly walking out of the depths of Waterfall and out into a path surrounded by open air on both sides. The path wound off to into another cave in the middle of a craggy hill. Frisk frowned as the wind howled and tossed their hair around while Flowey ducked behind their shoulder to get out of the brunt of the wind.

This… feels familiar. And then, a memory fell into place, ending with them glancing up to seeing Undyne glaring down at them from the top of the mound. Frisk shuddered.

*You know you are walking into a trap.

Well, forewarned is forearmed, right? At least they didn't see any bloodthirsty human hunting Captain of the Overlord's Enforcers up at the peak. Squaring their shoulders, they started walking forward. "Flowey, on the off chance that Undyne does show up and try to murder me in the next few seconds, would you like me to put you down on the ground? We could meet up in Hotland later."

He craned his head around so he could send them a disgruntled, nervous look straight into their eyes. "What the hell kind of question is that?"

"A possibly pertinent one?" They were nearing the bend in the path and no sign of Undyne yet. Maybe they were being paranoid?

Flowey rolled his eyes and started to slink back around their shoulder. "Yeah, well, you're being really cocky. What makes you think that if Undyne did start to chase us—FRISK! Duck!"

Without a second thought, Frisk crouched as low as they could manage. A blood red magic spear slammed into the ground before them after nearly slicing through Frisk's head. Watching in mute horror as the spear fizzled out of existence, Frisk gulped and then turned to look over their shoulder.

Undyne stepped out of the shadows of the exit they'd just stepped out of—she must have been waiting in the shadows as they walked past her. Again, she had her helmet off and it appeared she'd left it someplace. She grinned at them and laughed. "You have quick reflexes, human. Good! Then this should be fun."

Frisk straightened from their crouch, never taking their eyes off her. After a long moment of silence, Frisk considered their options and took off at a dead run for the cave entrance.

A volley of red spears, blocked the path; Frisk nearly flopped onto their back, trying to stop themselves from running into them. Their soul appeared before them and they heard the loud thump of Undyne landing behind them. Tossing themselves to the side, they barely missed the spear she'd flung at their back.

Staggering in a circle around her, they backed down the path, hoping to get more room to move. Undyne only laughed at them, her one eye tracking their clumsy movements. "Are you really going to be dancing around me this whole fight, human? Alright, little coward, let's see how long you can last doing that!"

"Frisk," Flowey whispered against their shoulder. "You can't keep running away."

Frowning, Frisk fell into a defensive crouch and watched as Undyne summoned another wave of spears. Gazing at them, they nodded to themselves. "Alright then. So I won't run away."

*Your enemy stands before you. Facing your opponent head on fills you with DETERMINATION.

"Oh? Finally standing your ground? Brave, but dumb. Here, human, catch!" She pointed in their direction; the spears shot to them.

Ducking to the side, Frisk reached out and snatched a spear out of the air. Instantly, their heart turned green; they let the momentum of the spear whirl them around into a circle, rather than fight it. When they wheeled around back forward, they had the spear securely in their grasp and pointed at Undyne.

For a moment, Undyne actually looked surprised. Then she tossed her head back and howled with laughter. "Oh, the human can fight, can they?" When she had herself under control, Undyne gazed at them with an easy confidence. "Okay, human, I'll give you credit. First, you have the gall to actually try to get through the Underground without killing anyone, flaunting our most fundamental law. Then you try to break up your little party with that little shit kid and made me give up my prey! And now, now you have the audacity to point my own spear at me! Even though you're a coward trying to practice some goody-two-shoes shtick, at least you're not completely pathetic. Okay, human, you want to die like a real opponent?" She summoned more spears, all pointed dead at Frisk. "Then let's see you move."

"I hope you know what you're doing," Flowey mumbled before ducking into the back of their shirt.

"You've got this," whispered the voice of an old memory. Cold hands corrected their grip on the energy spear and nudged their feet apart. "The first step in winning any fight is facing your opponent dead on. Show me your war face, Frisk."

Frisk gritted their teeth and tightened their grip on the spear, feeling the magic shift like running water beneath ice. If they focused on that feeling, it was almost like practice back when they were young. Even this strange version of Undyne could pass for their old friend if they ignored the killing intent in their aura and focused on that wild grin. "I've got this."

Undyne only grinned wider. "Then show me. Die!"

The first wave was child's play—high strike, low, twist to the side to deflect a low strike, turn back in time to catch another high strike. As the wave ended, Frisk knew she was only trying to feel them out. It was what their Undyne always did first whenever they'd gone sometime between training. So, either she was more interested in having a fun bout, or she was playing with Frisk. They hoped it was the former.

Another wave sent them twirling—eight spears this time, high front strike, low strike on the left, mid strike back on the right, high then low from the back, swing around to the front for another high strike, then two mid strikes from either side that came so fast that Frisk nearly missed blocking them in time. The green magic pinned them in place, but its unusual side effect meant that they weren't dizzy at least. Still, with the wave over, they had a chance to talk. "Hey, don't you think this is going to get boring fast if we just do this all day? Maybe we could-"

"Oh, bored already? Then take this!"

Frisk grimaced—that wasn't what they'd been going for.

Twelve strikes, including two feints that almost Frisk speared through the back. As they turned to stop the second to last spear, Flowey screamed at them. "Frisk, behind you!"

Frisk barely got turned around in time to see a black spear ripple through the shadows, only the faint gleam of magic giving it away in time for them to block it. As the spear vanished, negated by the other spear, Frisk turned to glare at Undyne. "That was hardly sporting."

Undyne only smirked. "That's funny—do you think I give all my prey 'sporting chances'? Do you give your meals time to run away? Cause that's all you are in the long run, human. Once I'm done with you here, I'm going to rip that soul out of you and take it to the Overlord. Then he's going to finally break the barrier. That's all there is to it. Humans—as if any of you deserve the chance!" She lifted her arm, palm up. A ring of spears surrounded Frisk, not coming from just four angles but at least twelve.

Frisk's heart hammered in their chest—this wasn't a technique their Undyne used often. The first time she had, she nearly stabbed Frisk through the head. Asgore had caught them that time and tried to firmly lecture the fish warrior on safety, ending with the threat that if he caught her trying it that he'd tell Toriel on her. But that didn't mean she never used it again, nor did she forget to show Frisk the best way to block it—they'd just had to get sneakier about where they practiced. Shifting her hands down near the end of the shaft, she waited until the first spear started to move. There, at the eight o'clock position, that spear moved forward, followed swiftly by the one at the nine o'clock position and then the one at the ten. Gritting their teeth, Frisk spun around and lifted their spear—their spear smacked against the first spear, causing it to shatter, and then followed the arc of their swing, smacking into the next spear and the one after that until Frisk had completed the circle, smashing each spear as they turned. The spear in their hand flickered and hairline cracks formed along its length; it would not survive another hit.

They forced themselves to turn back to face Undyne and tried not to pant in front of her. "You know, I'm starting to think you don't like me very much." When she started to laugh, Frisk took their chance and hurled the spear back at Undyne. It was too weak to do more than take a sliver of HP if it did hit, but that was not their intention—it sailed through the air true, but Undyne only frowned as she swatted it and it shattered.

More importantly, the moment Frisk let go of the spear, their soul turned red again; while she was distracted with the incoming flying missile, Frisk darted past her and dashed through the cave entrance.

Undyne roared angrily behind them; Flowey laughed as they slipped into the shadows. "Yeah! In your face!"

Frisk might have smiled, but the heavy footfalls behind them kept them racing as fast at they could. Gotta get to Hotland! She won't fall for that trick again! Maybe if they got to Hotland, she'd overheat from the exertion. The problem was getting her all the way to Hotland without her catching up with them. Considering she was probably being weighed down nearly as much in her armor as their Undyne had been, it was a helpful handicap. The problem was, one, it sure didn't seem to be slowing her down, and two, they had no idea if she was perhaps faster than their Undyne.

That said, she sure was about as pissed as their Undyne was. "Human, get back here and face me!"

A bright red laser shot through the shadows behind them, dancing wildly around them. Stalactites fell from the ceiling, dropping down on the ground around and to the river below. Frisk yelped as one landed perilously close to them. Glancing over their shoulder, they saw the laser was actually coming out of Undyne's eye socket. She'd yanked her eye patch off to reveal not an empty socket, but some sort of device imbedded into her skull. Oh, my Undyne would love that.

*You watch as she shoots laser beams out of her eye socket.

*You are both easily impressed and distracted.

Flowey seemed just as surprised as they were. "She shoots laser beams out of her face?"

Undyne cackled. "A special gift from the Royal Scientist! Now why don't you just stand still and feel how powerful it is for yourself."

"Fuck that shit," Frisk muttered and ran faster. Their Undyne probably would have told them to "watch their fucking mouth" if she heard them say that.

Up ahead of them, they saw the marquee sign welcoming them to Hotland. Frisk shot past it and escaped out of the cave. Looking ahead, they glanced to the side and saw Sans at his station, gazing at them, red eye huge in the socket. Wishing they had breath enough to shout for help, they only risked a single wave as they shot past him. One of Undyne's spears nearly shattered the right side post of his station.

"I'll kill you later, Sans!" Undyne roared as she also ran past him.

Frisk frowned—she sure didn't sound winded. Taking a glance over their shoulder revealed that she looked perfectly fine as well. Even when they ran past the water cooler, she looked as fresh as she had at the start of the fight.

Caught up in their worried musing, they almost missed their phone start to ring. Without a second thought, they answered it. "Hello?"

Flowey screamed. "Are you joking?"

Undyne wasn't amused either. "You little fucking shit! HOW DARE YOU pick up a call while I'm fighting you! GET BACK HERE!" She sent a wave of spears so densely packed that Frisk nearly slipped off the edge of the path trying to evade it.

"HUMAN!" Papyrus's voice shouted in their ear. "I just got a text from Sans saying you were being chased by Undyne."

"Uh, yeah, that's about right." They hopped to avoid another spear aimed low. Up ahead, they could see the roof of Alphys' lab. Something told them that they weren't going to receive any help if they tried ducking in there now. "Look, I can't keep talking, Undyne's gonna-"

"Did you think that because she's a fish that Undyne wouldn't be able to handle fighting in Hotland? Well, you used to be right! However, the Royal Scientist made her a climate controlled suit of armor! So, no matter where you go, Undyne will always be in top form to fight you."

"Ah, christ on cracker."

*That puts a damper on your plans.

"Listen to me, human! There is no running from Undyne. If you want to defeat her, then there is only way. You must turn and fight her."

"I don't want to hurt her," Frisk gasped, weaving to the side to avoid another spear. The lab was looming ahead of them now; Frisk made a snap decision and headed south at the crossroads.

"Oh, please, you couldn't if you tried," he scoffed. "But that doesn't matter. If you can fight her to a standstill, she might be impressed enough by you to not kill you immediately."

Frisk nearly tripped avoiding the laser as it swung dangerously close to them. "You think I can talk her around?"

"Of course not! Just dump her in the river there ahead of you." They didn't bother to ask how he knew they were running up to the river where the Ferryperson usually waited. Lord only knew how many times their own Papyrus pulled that trick. "It won't kill her, but it's very hard to swim in armor, you know. While she's busy, you can run and find a place to hide like the coward you are!"

Frisk's eye twitched. "Thanks a lot, Papyrus."

"No need to mention it, human! Now, stop being a baby bones and face her!" With that, he hung up on them.

Standing before the water's edge, Frisk snatched the nearest spear out of the air and used it to ward off the other spears. Their soul glowed green before them again. When Undyne saw that they were standing their ground, she skid to a halt.

"Finally! Cowards like you sure can run fast, huh?" she hissed, barely out of breath.

Frisk didn't even try to hide how their own chest was heaving as they stuffed their phone into their pocket and gripped the spear. "My training instructor was very strict when it came to leg days."

Undyne sneered at them. "Smart person. Too bad their wisdom didn't wear off on you."

Leave it to Undyne to accidently compliment her own training regime; Frisk bit their lip to keep from smiling. "Yeah, that's what she said. A lot."

"What a pity for her, then, to have you for a student." She raised her hand and summoned another ring of spears.

The attack came from the five o'clock position and went clockwise again; Frisk whirled around, smacking as many as they could, but the last slipped through and slashed their arm, knocking off five HP. Frisk grimaced and stood their ground, pointing the spear back at Undyne again. Maybe they needed to try something different. "So, you'd call me a bad student. What kind of student would you want to train?"

Undyne paused, hand jerking to the side so that the spears she'd started to summon flew wide. She scowled while Frisk stayed in their spot. "What the hell kind of question is that?"

"A curious one? If you're really going to kill me and take my soul, then at least indulge me first." C'mon, haven't you seen enough anime at this point to know a good chance to monologue when you see one? Their Undyne sure loved her chances to monologue.

Shaking her head, she summoned sixteen spears and sent them flying in waves. While Frisk tried to avoid getting impaled, she turned their tactic around on them and began to talk as the spears flew through the air, distracting them so they missed two of the spears and wound up at half their health. "If I had a student it wouldn't be no wimpy, 'give-peace-a-chance' drivel spouting moron like you."

Panting hard, Frisk considered their options and instead reached into their pockets and yanked out one of their sea tea bottles. They wrestled the cap off with one hand and downed the bottle in a deep draught, healing themselves almost to full health and sending a tingling feeling through their whole body. They tossed the bottle to the side, away from their feet. It'd be embarrassing as all get out if they accidently killed themselves by tripping over their own trash.

Rolling their shoulders, they fixed their grip on the spear. "That's not a real answer and you know it."

Undyne snorted and formed another wave, but this time she looked thoughtful—the look did nothing to ease their worry. "Tell you what. You stop acting like a little bitch, maybe then I'll talk to you. Until then shut up!"

At the jerking motion she made with her hand, another ring of spears, eight in all, four aiming down from high and four aiming up from low, appeared around them and then shot forward.

Frisk's first thought was simple math—they could easily block four spears at once from the front and take the rest to their back. As long as they could tank the attack, they could try and heal again. If they took the attack straight to their soul, however, they'd be dead in an instant.

The second thought nearly made their thought stop. They could, in fact, tank the hits—but Flowey, still clinging to the back of their shirt, could not. And there was no resetting for him anymore with them in this world. They couldn't duck either as he'd still get hit from the spears aiming down at them.

Without another thought, Frisk removed their left hand from the spear and whirled the spear around behind their body, getting it up and level just in time to block their back and Flowey from those spears. At the same time, the four spears in front slammed into their soul.

It cracked and shattered into pieces.

*But it refused.

The pieces slammed back together and Frisk fell to their knees. The spear they'd been holding crumbled, but Frisk was more concerned about controlling their racing heart.

"Frisk! Frisk, oh my god, are you alright?!"

*It appears you have enough determination to truly refuse death.

*You decide to worry about what this means later.

"Frisk!"

Closing their eyes, Frisk marshaled their courage and forced themselves to stand. "I'm fine, Flowey." When they opened their eyes, they felt hot. "We're not done here."

Undyne looked at their face, but whatever she saw there gave her pause. After a moment, she tossed her head back and laughed. "Well, I guess there is something more to you after all." Reaching up into the air, she summoned another spear into her hand. Casually, she tossed the spear at Frisk, not aiming to impale them, but a casual toss that Frisk caught easily. Warily, Frisk adjusted their grip on it, their blood still singing from the sea tea. "Alphys told me that you humans are able to pull out some real interesting tricks. Things that seem impossible, like miracles."

Frisk wondered what she was getting at. "I do believe in miracles."

Undyne smirked and summoned another wave of spears, this time all aiming at their front. "Show me."

Bracing themselves, Frisk obeyed. Wave after wave of spears, round after round, they did their best to protect themselves and Flowey from Undyne's onslaught. There were some close calls, Frisk used up all their healing items—but then holes started appearing in Undyne's defenses. At first, Frisk ignored them, assuming they were traps. But as the fight dragged on, Frisk took a risk and struck back—twisting about, they swung the butt of spear against Undyne's side. The armor rung but it barely took off any of Undyne's health—still, for a moment, the fish seemed honestly rattled. Then she narrowed her eyes at them.

Undyne attacked again, but this time, there was another hole in her defense.

Frisk studied her. She's baiting me—for what though? Frowning, Frisk ignored it. "Undyne, we don't have to keep doing this-"

The fish growled and attacked again, relentless. A round later, there was another hole in her defense.

What is she up to? Frisk decided to play along.

A new pattern emerged—Undyne would leave a hole in her defense, Frisk would attack it but never do serious damage. Undyne would renew her attacks savagely, but then another weakness in her defense would appear. Each time, Frisk noted with dread, the weakness was aiming for more vital spots.

Is she trying to get me to kill her?

*Or rather. Is she trying to make you a killer?

Frisk shuddered and refused to take the shots.

Round after round passed; Frisk was starting to feel jumpy and twitchy from all the sea tea in their body, like they were buzzed off energy drinks. I don't even like energy drinks, they thought fuzzily. Shaking their head, they leveled their spear at her. "Undyne, this is getting ridiculous."

"What's a matter, human?" Undyne asked, wiping her mouth with the back of her hand. Had her voice sounded so raspy before? They weren't sure, but they hadn't thought so. "Don't you want to have one of those epic battles that go on for days on end, stretching on until we go down in the history books for this duel?"

Frisk grimaced; that definitely sounded like something their Undyne would say and definitely because of some anime Alphys had shown her. "If it's all the same, I have to eat some time. God, is this what you and Papyrus do together for fun? Fight each other?"

Undyne blinked at them. "What? Yeah, mostly."

God give me strength, these monsters are going to put me into the grave one way or another. I took a three hour nap and I'm already back to being tired. "So you… train together?"

"Train together? Nah, I have to train my subordinates. Papyrus I just fight for fun. That bonehead could teach a thing or two to those idiots I have to whip into shape."

Remembering how eager to attack the Canine Unit had been, Frisk wondered just what she was whipping them into shape to do. Still, she had Undyne talking—she didn't dare let up now. "Are you two friends then?"

Undyne snorted, but suddenly seemed to have trouble meeting Frisk's eyes. "I'd trust that skeleton as far as I can throw him."

Frisk raised an eyebrow. "He's a skeleton and you're you. Doesn't that mean you'd be able to throw him pretty far?"

She laughed, as if delighted by the mental image. "Hell yeah, I could! I could toss him from one end of the Underground to the other if I wanted."

"So… that means you actually trust him quite a lot then."

She blinked, scowled, and then summoned another wave of spears. "More fighting now."

After a brutal sixteen spear assault, Frisk tried their luck again. "So, how do you and Papyrus know each other?"

"Seriously? Are you really—oh, fine. He tried out for the Enforcers, alright?" She summoned another wave of spears.

Panicked, Frisk talked fast. "O-oh, hey that reminds me! Why does he call it the Royal Guard if it's really the Overlord's Enforcers? And why not let him if he is your friend?"

"He is not my—augh, you little shit! Fine, you want to talk?" she waved her hand and all the spears disappeared, including the one in Frisk's hands. "Fine. He calls it that because that's what he thinks it is. He thinks it's such an honor, that is so much better than being a sentry. That we're protectors and defenders of our people. And that's exactly why I won't let him in yet!"

Frisk frowned, baffled but hopeful. "If it's not what you do, then what do you do?"

"Terrorize people mostly," Flowey muttered behind their shoulder just as Undyne said the same thing before them.

"We carry out the Overlord's will," Undyne answered, her eager, brash energy ebbing fast as her eye gazed distantly at the river behind them. "We do as he says—arrest a dissenter here, relocate someone there. Execute someone if we must. And because of what we do, people turn a blind eye to our members'… antics." She growled the word out between gritted teeth. "No one outside the Enforcers can stop the members. Only by working on the inside has any progress been done."

Frisk shifted, both brows going up. "Progress? Did you join… to make them clean up their act?"

"Clean up their act? I'd be happy if they'd just stop murdering each other."

Frisk fought the urge to blanch. "Oh."

"Oh is right. Tell me, human, how long do you think either of those skeletons would last if I let Papyrus in? Maybe a week? The moment Sans opens his big mouth, the only thing keeping him alive would be Papyrus. And that overeager idiot can't be everywhere to save his brother's backside."

"So, you're worried about both of them? Or just for anyone who might end up as collateral from the Enforcers?"

Undyne stared at them for a moment before she began to laugh—not raucously, like before, but more of a restrained mirth. "Look at you, trying to get me to tell you all this useful shit, like you're going to use it against me—or worse, like you're trying to befriend me." She paused again and shook her head. "I'm not your friend, human, and I never will be. I don't know how you got on Papyrus's good side, but it won't work for me."

Anxiety slammed Frisk in the gut. Oh god, what if she turns on Papyrus—what if she suspects that he-? No, get it together, Frisk. They cleared their throat. "Why do you think I'm on Papyrus's good side? He was trying to help you capture me, wasn't he?"

She glowered at them. "Don't take me for a fool, human. I know that idiot," she paused, frowning thoughtfully. "Which is how I know he's never going to cut it in an organization like the Enforcers—not as it is now. There's still too much work to be done. Look, you want to befriend someone? To help them? Go bother him. Convince him to give up on this Royal Guard shit."

Frisk sighed. "I can't do that. He… he's got too much riding on this, I think. It's how he thinks he can get a brighter future."

Undyne grunted. "He would." She shook her head and ran a hand over her hair, an old gesture that Frisk recognized, one that meant she was irritated and impotent to do anything about it. "So. Then he's just going to have to wait until I can finish reforming those idiots. I'll just have to keep him distracted for now." She paused and frowned thoughtfully at Frisk. "Which maybe you can help with. Tell you what, human—I think I might have an actual use for you. Keep distracting that idiot for a while. Then maybe I'll just forget we ever had this little talk."

"I… think I could manage that." Their soul, however, didn't disappear—Undyne wasn't done with them yet, apparently.

The warrior regarded them for a long minute before shaking her head. "You really are a strange creature, human. You befriend Papyrus, you try and even befriend me. You talk like you give a shit about monsters. You, you even saved one, back there on the bridge. I just don't understand you." At last, something like satisfaction touched her eye. "You're changing things around here. Maybe you can even change Asgore some."

Finally, the powerful tug on Frisk's soul let up—Undyne was sparing them. Quick to act, Frisk returned the favor and dropped out of their defensive posture.

"Now get the fuck out my sight," Undyne said, as she turned around. "Go to Snowdin. Go to Hotland. I don't care." She paused and glanced back over her shoulder. "But if you do go to Hotland, you'll definitely find yourself having one bad time. Got it?"

Frisk nodded, too unsure to risk offending Undyne before she was gone.

"And pick up your goddamn litter before you leave. This isn't the dump." Turning her head back, Undyne left them.

Once she was gone, Frisk sank to the ground and sighed in relief. "Oh my god."

"Holy crap," Flowey murmured, rising out of his hiding to look where Undyne had left. "You… you actually survived a fight with Undyne. I… I don't think anyone other than Asgore could have managed that nowadays." He reached idly the hair that hung next to him and began to tug on it, like he was ringing a bell. "Holy crap, Frisk! You actually went toe to toe with Undyne and lived! You didn't die once." He stopped yanking on their hair to look wonderingly forward. "Maybe miracles do happen."

Frisk didn't know whether to laugh or sigh in irritation. "Thanks, bud. Appreciate that."

"You know what I mean," he insisted. He stared up at them as they calmed themselves down. "Are you ready then? To go to Hotland?"

Taking one last big breath to steady themselves, Frisk forced their body to stand and lifted their chin. "Yeah. Let's get going." They took a few steps forward before pausing and looking back. "Uh, but first, I think I better clean up that trash."

---

As a response to Geust, from the kind reviews they left on the last chapter:

I only mentioned the log in thing because that way I would be able to get in touch with you faster so you won't have to wait so long for replies.

Whenever I look at Shyren, to me it looks like she's floating a few inches off her agent's shoulders—I don't think she sits directly on them in game, which is why she doesn't have any negative effects in this story. I don't recall her agent attacking during her fight, so whatever attacks it has is a mystery, but in this Fell universe, they have acid because, well, why not?

Flowey is aesthetically different from the game, just less noticeably so—he looks really raggedy and a little chewed up, even after Frisk fed him Monster Candy. He's also nicer here, but that's because this Flowey hasn't been resetting a lot—he's been too afraid of getting murdered by everyone that he hasn't had a chance to get bored yet.

I can't really take credit for Flowey's emotion work around—when Flowey mentions in the game that he found he didn't want to die, it just sounded to me that he became afraid of not existing. Fear keeps us alive, but so does hope—they're both tools for survival. Something prompted him to keep resetting in the backstory of the game, and he obviously felt hope too because he leaves Asgore to join Toriel, hoping she'd prompt emotion from him. So, in this story, Flowey does feel both fear and hope; whether or not he actually does in the game is up to debate.

As for what's up with the Bone Bros or Gaster—well, spoilers.

And, aw, thank you—Undyne didn't really come naturally to me, so I wasn't sure if anyone would care for how I wrote her. As to why she didn't have her helmet it on, two reasons. One, and this is very silly, but actually true—I see so little fanart for Fell!Undyne with her helmet on, I tend to forget about it. In game, she yanks it off for no reason too, so I'd recommend not sweating too much over it. In this story, she probably took it off because she got annoyed searching for Frisk and decided she didn't want to impede her (already hindered) vision, so she took it off. Secondly, as you see in this chapter, she can shoot lasers out of that empty socket, so might as well leave it off.