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The Fallen Man

Summary:

EDITED 12/4/25: This fic won't be finished, so I have updated the chapter count to reflect what was written, along with putting it into a collection that it will not be updated. Thanks to everyone over the years who has read this fic, and thank you for your understanding. 💖

While adventuring one day, the TARDIS takes The Doctor to the Underground of Mt. Ebott, in the year 201x. Or something to that effect; he isn't really sure. His ship leaves him behind in a moment of fear, leaving Ten stranded and wondering: Why is he here? Who are these Monsters? Can he help them? And, most importantly, can he make it through the Underground without hurting anyone?

An Undertale and Doctor Who crossover where the Tenth Doctor essentially does what would amount to a true Pacifist run. More tags will be added as characters are introduced in subsequent chapters!

Minor Undertale spoilers in the story and MAJOR Undertale spoilers in the Author's Notes, so be warned!

A gift for my IRL friends Brandon and Cece. I hope you both like it!

Will be posted both on Tumblr and here simultaneously. Tumblr link here! http://timeywimeyten.tumblr.com/post/135692661219/the-fallen-man
Thanks for reading!

Notes:

This fic is a Christmas gift for two of my IRL friends, Brandon and Cece. Thanks for everything, you two! I hope you both enjoy it. Thanks for proofreading it for me, also!

Anyway. This fic does contain minor (and, later on, MAJOR) Undertale spoilers, especially for the Pacifist Run. I just wanted to warn you all!

I hope you all like the fic! It was interesting, trying to take the world of a fantasy/sci-fi game and transporting it to the world of "Doctor Who". So, I tried my best to make sure that some of the more fantastical elements were retained, but with some scientific flair. After all, don't worry--it will all be explained later, in susequent chapters (and when I have even more time to ponder some of the minutiae of plot points)!

Tumblr link here, for anyone curious: http://timeywimeyten.tumblr.com/post/135692661219/the-fallen-man

Enjoy the fic!

(See the end of the work for more notes.)

Chapter 1: MT. EBOTT, 201X - The Fallen Man Falls

Chapter Text

                  It was one thing for the TARDIS to disappear; it was fully another for her to flee upon landing. Sadly for The Doctor, he’d gotten out of his ship, which had then decided to ditch him in the underground below what the navigation system had called Mt. Ebott. Why he’d gotten there was a mystery, but he soon realized what had made the blue box leave so quickly: The air reeked of paradoxes and timelines prematurely cut.

                  Or, ‘reeked’ wasn’t the word… A more appropriate way to explain was that the anomalies were obvious to Ten, riddling the air with a kind of bizarre vibe, for lack of a better term. Time Lords could sense these things—after all, they didn’t have Time-based abilities for nothing—and, of course, so could the TARDIS, who got indigestion from things and places like this. Last time had been with Donna Noble on that Christmas night with the Racnoss, a runaway bride, and an unlikely friendship. Those Huon particles had made the TARDIS feel quite ill. It was the same principle—except this time, his ship must have felt incredibly sick. No wonder she’d taken him here—and then ran off. The question was, how had the temporal anomalies happened?

                  The Doctor pondered this as he stood there, his thoughts interrupted by the realization that he was stepping on a perfectly good patch of buttercups. Ten scrambled forward and decided to check his surroundings. Black walls, gray flooring, and… A path. The Doctor decided to follow it, entering the next room.

                  There was a decorative green carpet on the cavern floor. Nothing how fishy it was that there was a carpet in the middle of a place like this, The Doctor moved forward, inspecting the rug with suspicion as he pulled his brainy specs from his pocket and put them on. He leaned down, realizing as he approached the carpet that it was actually a small, incredibly conspicuous patch of grass. He with his nose just barely above a blade of grass, a flower popped out of the ground, a smile on its face. Ten staggered backward, letting out a cry of shock. “Blimey--!”

                  The flower's light gold petals contrasted starkly with the darkness surrounding it. “Howdy!” It began, in a bright, joyous voice with a beaming smile, “I’m Flowey! Flowey the Flower!”

                  Ten, who’d managed to fall onto the ground in his surprise, was a bit speechless.

                  “Umm. Sir? You okay there, buddy?”

                  The Doctor nodded. “Sorry, I just—I wasn’t expecting a flower to come out of nowhere! Where did you come from?”

                  “Oh, it’s not a big deal! Don’t worry! I love surprising people! Especially visitors. So!” Back to business he went. As The Doctor stood up, Flowey went on, tilting his head upward to better face the visitor. “You’re new to the Underground, aren’t’cha? Golly! You must be so confused. Someone ought to teach you how things work around here!”

                  “I’d appreciate some background, yeah,” Ten admitted. “I just kinda managed to stumble down here! You seem to be more of an expert than I am, really. Thanks, Flowey.”

                  Flowey chuckled. “Aww, shucks! Well, I imagine it would be better if you had an all-knowing guide or something like that to show you the ropes, but I guess lil’ ol’ me will have to do.”

                  Ten had to admit, for a place where he was stranded, the Underground beneath Mt. Ebott didn’t seem too bad. After all, there were odder things than chipper talking plants!

                  “Oh! I haven’t introduced myself, have I? I’m The Doctor. ‘s a pleasure.” In lieu of shaking hands, he waved. “An’ yeah, I am new ‘round here. Just got here a minute or so ago. Mind fillin’ me in, then?”

                  “My pleasure!” Flowey beamed, his voice almost too saccharine to be believable. “Ready? Here we go!”

                  Nothing changed at first; but, slowly, the lighting around them dimmed and shifted, which had somehow made everything look washed out. Grayscale, if that were possible. How odd. Pocketing his glasses, The Doctor wondered what was going on. Must have been something with bioluminescent crystals or fungus… But, before Ten could ponder any further, Flowey began his primer.

                  “Now, here in the Underground, we wear our souls on our sleeves. Literally! So, whenever we encounter each other, our souls glow! I know you can’t see it, since you’re human, but your soul is glowing too! It looks like two hearts to me. Which is…” Flowey paused, a crack in his cheerful veneer. “Hmm. Odd. Never seen a human with a two-hearted soul.”

                  There was a silence; something in the atmosphere of the room grew heavy, weighing on The Doctor’s hearts. But, that was probably just him being paranoid.

                  Before Ten could explain to his guide that no, he was not human, Flowey barreled along in his speech. “Anyway! Here in the Underground, we start off with weak souls, but we can grow strong if we gain a lot of LV. Why, what is LV, you ask?”

                  “Hmm, I dunno, sounds like an abbreviation for ‘level’?” This sounded suspiciously like a video game’s tutorial to The Doctor. Had he literally walked into a video game? Nah. That would’ve been too bizarre. But, to be fair, there was a talking flower sitting there before him. Things probably worked differently around here than on other planets he’d visited.

                  There was a hint of condescension in the plant’s tone. “No, silly! It stands for LOVE, of course! You want some LOVE, don’t you? Don’t worry, Doctor, I’ll share some with you!”

                  Flowey winked, and suddenly, white pellets filled the air around him. Floating seeds. Or, what looked like seeds; The Doctor was standing too far away to tell what exactly they were, as he’d moved backward during the course of all of this. He pondered how the pellets were flying—telekinesis? Probably.

                  The amiable guide explained, “Down here, LOVE is shared through little white ‘friendliness pellets’! See, they’re floating right now!” Flowey gestured with his head towards them. “C’mon, Doc, move around, and try to get as many as you can!”

                  The friendliness pellets looked unnervingly like bullets, now that they were heading straight towards The Doctor. He instinctively dodged them, dashing out of the way with an unintentional flourish.

                  Flowey’s smile dropped a bit, but he still went on, with a subtle exasperation in his words. His voice fell in tone, losing a bit of the sweetness and sounding similar to a tired, underpaid tour guide who’d given the same tour twenty times in the same day. “Hey, buddy. You were supposed to catch the friendliness pellets! Let’s try again.”

                  The Doctor hesitated, scooting towards the exit of the room. “Erm, Flowey, I think I’ll politely decline--!”

                  Flowey tried again, and this time, Ten hit one of the friendliness pellets with his arm as he tried to evade it. Pain shot through his limb, and clutching it, he stumbled backward. “What the hell what that?” While The Doctor nursed his arm, rubbing it gingerly, he could hear a maniacal laugh.

                  “You idiot.”

                   The plant’s face grew sinister, his mouth filling with large, sharpened teeth. His eyes turned vacant, as if they were gouged-out holes in the face’s surface. It was a nightmarish sight.

                  “It’s kill, or be killed. Why would anyone pass up an opportunity like this?”

                  The bullets rose from the space behind Flowey, creating a ring in the air, sinisterly spinning. He let out an evil cackle. “Die.”

                  Ten had imagined many scenarios with his own death, but “death-by-homicidal-flower” certainly hadn’t been one of them. As the bullets closed in on him, he cried out for help. A white flash dashed around in the background, followed by a fireball, which threw Flowey out of the way—and, seemingly, out of the room. Its owner wasn’t far behind. The lighting returned to normal, and everything grew brighter once again.

                  Moving into the area where Flowey had once been, a grand woman appeared. The Doctor wouldn’t have described her as anything but; she embodied grandness, both in her regal, gentile air, and in her height. Yet, she also exuded humility, even with the gorgeous purple robes she wore, which had what appeared to be a sigil or rune of some sort on them. The ensemble contrasted greatly with her fluffy alabaster fur.

                  The Doctor’s rescuer had small horns, red eyes, and floppy ears, and to an untrained eye, she looked like a combo between a bear and a goat. But, Ten couldn’t really place what she was. Not that it mattered; she seemed genuinely friendly, unlike Flowey.

                  The stranger bolted towards Ten with a concern on her face and a gentleness to her tone. “What a terrible creature, torturing a poor, innocent—“

                  She stopped before him. “—Youth…?” The goat-woman gave The Doctor a puzzled look, eyebrows furrowed. After a silence, she said frankly, eyes squinted in suspicion, “…You are not a child.”

                  “Nah, I’m an old man, but some say that I’m no better than a child. Still, thanks for saving my life there, ma’am,” Ten managed, the pain starting to go away on its own. He got up before asking hesitantly, “Erm… What’s wrong?”

                  The woman shook her head, as if to clear her thoughts. “Oh, it is nothing! It is just—” She put a clawed paw to her cheeks, an embarrassed blush standing out against her fur. “It is just that you are the first adult who has fallen down in a long time. Usually, when someone falls down in these parts, they are children. I am so used to saying ‘child’!”

                  The Doctor wasn’t sure whether this was sweet, or sad. His finger was on ‘both’. Still, that was also suspicious. Talking flowers, fallen children, and now, one of the locals appearing. Things were getting interesting.

                  The woman went on. “Still, sir, do not be afraid. I am Toriel, caretaker of the Ruins. And you are?”

                  “The Doctor,” he replied, offering her a grateful hand.

                  “Well, Doctor, it is a pleasure to meet you!” She shook his hand politely, yet not without enthusiasm. “You see, it is fate that I saw you here—I come to check the Ruins every day, to see if someone has fallen down. You are the first human to fall down in a long time!”

                  “Erm, Toriel, I’m not—“

                  But, Toriel seemed to be too enthused with the idea of a new visitor from the surface to take notice of Ten’s protesting. She cut him off. “Come, Doctor, let me guide you through the catacombs! This way.” Toriel walked away, but stopped at the door, turning around to see if The Doctor had followed.

                  Ten shrugged—after all, she didn’t seem dangerous—and commented while he went to meet her, “Oh, catacombs! I love catacombs! The most interesting kind ‘a combs there are. A hint hard to brush your hair with, though,” he joked, and she chuckled at the awful pun.

                  “Ooh, you like puns?” She asked, impressed. “I do too! I will have to tell one of my friends. He has a talent for puns.”

                  “He likes puns, I like puns, you like puns--!” The Doctor gestured as he spoke, and Toriel nodded. “I feel like we’ll get along swimmingly!”

                  “I should hope so.”

                  “So, Toriel, back to the catacombs: Have you ever seen the ones in Paris? They’re morbid, but they’re also marvelous, I tell you. Molto bene. You’d love ‘em.”

                  She smiled as if she were a mother listening to a child’s story. “I have not, but those catacombs sound interesting! I have only seen these catacombs, here in the Underground. Lovely, yes, but nothing like what lies above-ground, I would imagine! I have only heard some of the things that you are talking about while reading books that have fallen from above. You are clearly a traveler!” She had been looking away, but turned back to him, two canines—or were they fangs?—sticking out of her grin as she spoke. “Tell me more. I always love travelers’ tales!”

                  The two of them then left the room, entering the purple-tinged walls of the Ruins. As they departed, suspicions and concerns ran through The Doctor’s head. This was not normal. Something was definitely out of place here—and, based on the TARDIS dropping him off to deal with it, it was most likely his job to fix it. He dabbed his finger with his tongue, putting it into the air and then into his mouth while Toriel turned away, just to find the time period.

                  A bit earthy. A little metallic. There was a hint of oil, too, on the air. Add in the dampness of an underground cavern, cinnamon, and the smoke of a burning fire nearby, and it left an odd taste on Ten’s mouth. So, the year was probably… 2010-something. The temporal anomalies, as per usual, tasted iron-like—or, as some would say, like blood. The Doctor preferred not to think about that second option. Considering what kind of mess the local timeline seemed to be based on what he could sense, he couldn’t be sure. And yet…

                  When Toriel spoke, his uneasiness was assuaged. Maybe she could fill him in—without killing him—on what was going on beneath Mt. Ebott. After all, she genuinely seemed to want to help him.

                  If there really was something shifty going on in the Underground, then by all means, The Doctor was going to find it, goodness help anyone who got in his way. He resolved to resolve whatever kind of situation these poor people had gotten into. And, after all, he would need help, wouldn’t he? Toriel was the key. And, of course, her pun-loving friend. Whoever he was.

                  Still, seeing such a kind face in such a strange place… It filled The Doctor with DETERMINATION.