This was a special project requested by someone very close to me. I played through Undertale the April of this year, and found that my favorite character was Dr. W.D. Gaster. My take on his backstory hinges upon two setting-related factors: 1. The Great War occurred 1000 years ago. 2. The monsters dwelled within a Celtic environment, as befits the monsters that often seen in the game proper. As can be inferred, much of this will split off into headcanon, as it is my interpretation of the character. Due to the cast roster of the game being low, and this story beginning before, and running through, the Great War, several characters were of my creation.


A black cloak whispered by, stirring the pipeworts softly. Water, gray as the sky above it, rippled. Gaster glanced about curiously at the thick-leaved trees towering over the glade. He did feel somewhat out of his element, however, as it was quite different from the open moors he called home. His fingers kneaded the strap of the satchel he held over his shoulder. If he allowed his unease to win, he wouldn't learn a thing. He did, however, take reassurance from the fact that there were other monsters, other subjects of Asgore and Toriel, still dwelled on the fringes of the kingdom.

His mission was two-fold, holding importance both scientifically and politically. He respectfully knelt before the king and queen's thrones, his knee just barely touching the stone floor before Asgore quickly told him to rise as a friend. Toriel, leaning forward and gesturing forward Boann and her brother Lir, who stood on each respective side of the thrones. "Come, we have an assignment to discuss with you."

Walking along the covered stone walkways of the monarchs' dwelling, Gaster stared out at the reservoir that reflected the massive garden back at him. Stone by stone, Castle Fáilte was constructed at the turn of Anno Domini by Asgore's grandfather and his subjects. Shrouded in mist, it stood at the cliffside overlooking the ocean. Somewhere beyond the cliffside, Aeron, the third after Boann and Lir, respectively, in the royal guard's current roster, drilled the marine-based guards in the ocean.

The garden, a construction of Asgore's, sprawled outward, sporting flower bushes, designs of various monster life, most principally a Pegasus, kicking its front legs up in the air, and a few assorted trees and shrubs. Toriel's hand slipped into Asgore's, and Boann and Lir chuckled among themselves at a joke. It was Toriel who broke the silence. "Doctor, while you have been busy with your work, even you know that tensions between humans and monsters have been mounting."

Gaster nodded his head. "Yes, Your Highness, I have."

"Your current field of study, as your reports have told us, has dealt with weaponizing magic, correct?" Asgore inquired, despite the two knowing that Gaster's reports were often pored over by both monarchs.

Gaster shook his head. "That angle can be taken, sir, but it is more out of the interest in the field itself, specifically how it contrasts between monster and human magic." He reached up, and rubbed at the bridge of his nose. "Our technology is limited by our current time period, and admittedly, our magic can be a crutch for us."

"How so?" Asgore asked. Toriel turned her head in interest.

Gaster shrugged. "If we continue to use our magic to solve our problems, we will not technologically progress. Humans, being lower in magic, have had to adapt more along that route. We are simply growing apart."

Toriel nodded. "Hence, your assignment." Asgore handed a scroll over to her, which she held out to Gaster. Unfurling it, he saw that it had the king and queen's royal seals on it, and cast his gaze over it. "You will be continuing your studies into the field of magic, both human and monster, though you will be exploring more into fringe territory, that being the neutral areas between the lands of monsters and humans."

"The druids," Gaster commented, "As well as experienced magic users among our kind, who could live among them." He furled the scroll back up. "What are the implications?"

Boann's hand landed warningly upon his shoulder, but Asgore replied, "There are concerns we have about our world, Doctor. We cannot afford to lose our royal scientist at this point in time, and you have not been effectively trained as a spy."

Gaster grinned. "Ah, yes, I am a tinker. So a tinker like myself must investigate the fringe factions of humanity, as well?"

Toriel nodded. "Humans are divided as largely as monsters are, though we each live under respective kingdoms. If a common enemy is found, it will likely unite them."

Gaster nodded. "Very well, I understand. Have I any contacts?"

"You're looking at us," Lir replied, hitting him once on the back, "Should you have any issues, teleport back to us."

At Gaster's less than reassured expression, Toriel explained, "It is a self-contained community in that overgrown area, not so much out of spite, but more out of isolation."

"They could easily kill me, then," Gaster replied, but shrugged. "Then again, that's the risk I run in the field. Perhaps I've become too used to the ivory tower. I will create the means with which to protect myself."

Gaster clenched his fist as he descended past the nettles, knowing that he could easily summon his Gaster Blasters if he needed them. Created as a means of self-defense for his mission, he knew that their intelligence was highly limited, yet they were quite powerful for a few shots. Conjuring quietly, he created a spell to hide his figure, his cloak melting with the shadows. Due to the elusive nature of the residents of the area, it was likely that he would not see any of them, if he did not at first hide himself.

There were a few, he noticed, as he descended further. A female, her hair covered with a shawl, knelt to the ground, and carefully conjured the roots of a tree trunk, twisting them about into elaborate knots in the air. Further, a male with thick black hair and a beard, wearing a cape of thick wool, breathed out through his nose, and cast frost over the leaves and sticks upon the ground. These, however, seemed small tricks to Gaster, and he figured that these people were partly doing this to warm up their magic. As each instance featured an encounter with them alone, he moved on for the moment. The humans, however, seemed to be unaware of him, from what he could tell.

Above him in the trees, long-limbed monsters climbed, and swung, occasionally pelting the ground with leaves and sticks. He held his breath as one of them, his cyan eyes wide, swung down to stare right at him. Gaster stood still. The monster narrowed his eyes at the low light, but seemed not to register him, swinging back up and away, calling out to his compatriots above.

Pointed ears turned toward his steps as two monsters rose into view from behind a rock. A small fire crackled between them. Both were male, with the closer to him bore pale skin and dark blue hair, while the other had dark skin and long red hair. The blue-haired monster sharpened the tip of a dagger against a stone, while the other gestured upward with his hand, coaxing the smoke to rise, and hide them from view. Gaster wasn't sure if it was to hide them from him specifically, or from the sound of his approach.

He sighed to himself, knowing that his observations will likely take weeks. He opened his satchel, and took out the tablet upon which was written edible flora. At least he could teleport back to his workshop for the night, as it would be too dangerous at the moment to sleep in unknown territory.

The days slid by, with Gaster's tablets slowly filling from his observations over time. The humans and monsters slowly appeared from out of the trees. The cloaking magic was beginning to strain at him over time, causing him to waver slightly in his movements, and to sit, or kneel. The glade seemed to expand in size, revealing vegetation and pathways that had not yet been there before, the sunlight disappearing to mimic the night. Gaster's eyes brightened, purple light shining, as he generated his own light source from within himself. He bent his head, and half-crawled under the low-hanging branches, folding in on himself to avoid being caught. As he descended further, he saw shadows moving from out of the corners of his eyes, figures running past, and long limbs stretching. Chants in Gaelic and laughter sounded, surrounding him. Light burst forth from various angles as spells were cast in the distance.

Out of the distance rose a stone, glowing in a pale blue light. Falling over it, similarly to a spilling of oil, was a dark cloak, and above that cloak were two white hands that twisted the petals of a pale pink flower within them. Higher still, a skull hung in the darkness, with two yellow eyes glowing down upon the flower. The skeleton, having a softer, feminine voice, hummed to herself. Staring at her, Gaster understood how easy it would be to become lost in this glade, and forget about the land outside. It was strange to see another of his own type of monster, yet, in her listlessness, and in his lack of context as to this area, they were a great distance apart. His mouth opened to speak with her, but he covered it just as soon with a hand, deciding against it. He wondered, not for the first time, if perhaps the forest was opening to him, after judging him to be not a threat to the community. If so, perhaps speaking with her would seem too aggressive. On the other hand, would this not be the best choice for him, to first speak with someone who was similar to him? Then again, he chided himself, that could imply a racial preference on his part. Resolving to wait, he held his peace, though he desired to see her again.

He returned to his workshop upon teleportation, surrounded by shelves of books. A cauldron stood below the workshop's chimney, the fire out. Glass bottles, measuring devices such as a scale, and knives stood on a nearby workbench. A few star charts stood beside a telescope. A doorway led into his living quarters, holding a simple bed and a dresser. Further backward was a basin in which he could bathe. Near the entrance to the home stood a table where he could eat. Curtains covered the windows, muting the sunlight. Spent candles dotted the area. Gaster folded his arms, and stared at the scene. It was strange, how orderly it all was, with everything in plain view. He glanced at the telescope and wondered, not for the first time, how far humans had gotten in the field of technology, his lack of assurance making him uneasy. He had entertained the notion of speaking with human scholars, but the few attempts he had made had been lackluster, with the humans barring him more and more each time, finding his strange appearance unsettling, or concerning themselves more with lifting and looking at his limbs until he would eventually had to push them off with magic. There wasn't much that could be done at this point, he decided, picking up a wooden pail to take outside to the well, looking forward to a bath.

Boann and Lir, each grasping one of Gaster's arms, drew him further and further down into the darkness of the ocean's depths, careful not to drop him. The surface light slowly disappeared as they drew away from it, fish and algae brushing by his face. He shivered against the cold and the pressure, stripped down to his underwear to keep from soaking his clothing. Boann gestured to the right, and they bore him sideways, displaying to him more of the shadowed depths. Long limbs stretched ahead, and Gaster felt quite small as Onionsan swam by. Lir lifted his head, and kicked upward, Boann following to bring Gaster to the surface.

Gaster sighed from where he sat upon the beach, his cloak hanging over his shoulders like a blanket. Boann knelt beside him. "You still with us?" She asked.

He coughed, and nodded his head with a smile. "Just not used to the deluge. You are more used to the darkness than the light, yes?"

Boann smiled, tossing salt water at her leg, and rubbing her hands over her knee. Her soaked red hair hung over her shoulders in strings. Lir dove among the waves with a spear, sporting a line of three impaled fish upon it, the redness of their blood contrasting the grayness of their scales. "In a sense, yes, especially when we were first hatched far beneath sea level. In a way, we had to become used to the light, if we wanted to have a say in surface affairs. But, as you can see," she gestured to Lir, "quite a few of us are still more inclined toward the ocean." Gaster nodded his head, and stared out at the white foam of the waves as the sun set. "The darkness, however, Wingdings, is not home to you, but it is also something that merely exists, just as well as light. Don't venture too far, and don't let it make you forget about the outside world."

A white-haired man with a grizzled face and beard raised his head. Opening his hands, he released a cloud of lightning bugs that flew about, lighting the forest floor sporadically. Gaster's eye sockets widened, and he stared in wonder as they surrounded him, his writing tablet and quill slipping in his hands. "Monster," the old man greeted solemnly. Gaster drew back, but he added, "Yes, I can see you."

Gaster dropped the cloaking spell, but remained defensive. "I have not caused you any harm."

The old man shook his head. "Not as of yet, but your behavior is rather disconcerting. You have sneaked around this forest for a few weeks, and it disturbs us to know that we are being watched."

Gaster put a hand to his ribcage, bowing slightly. "Forgive me, but I am a scientist. I was merely conducting field research."

The old man rose, staring impassively at him. "Let us see how the others will judge that. Come along," he gestured, and the lightning bugs flew after him. Gaster, intrigued, followed as well. The old man, his name, when Gaster asked for it, being Dalaigh, led him into a clearing, lit by an eerie indigo light, illuminating the twisting vines and limbs of the trees.

Walking out from behind one of the tree trunks was a figure in a dark cloak, hood up. Gaster's breath caught as he recognized the yellow eyes that shined out from underneath it. Raising her hands, she lowered the hood, revealing a patchwork of scars about her skull, her searching gaze piercing him. Her eye sockets widened in recognition for a moment, only to narrow again. "Doctor Windings Gaster," she commented, suspicion plain to hear in her voice.

"The royal scientist?" A voice from above inquired, the speaker a crouching silhouette, "What is he doing here?"

"An ear, or an eye, of the king and queen, perhaps?" Another voice along the forest floor hissed in suspicion.

"King and queen?" A human, a young male with red hair and one strip of blue paint under each eye, emerged to glance curiously at the newcomer. Torchlight bobbed along in the distance, and Gaster felt uneasy.

The female skeleton waved an arm. "It is not your concern."

"He is within our territory. It is our concern," Dalaigh replied, "If it is your officials that have sent him, he is prying into our affairs."

She shook her head. "Allow us to speak with him. He is a scholar; we cannot be sure of his intentions."

"Be that as it may," another voice added, with the woman who wore a shawl entering, "we allowed him entrance into this forest, as he posed no threat. Perhaps we should not have made that choice?"

Webbed feet slapped as a scaled monster appeared, amber eyes glowing. In a hiss, he warned, "We have not judged the humans you have let inside, have we?"

The woman relented slowly, and the female skeleton held out her hand, beckoning. "Come, then, Doctor." Gaster followed her, feeling the eyes of the humans and concealed monsters upon him. She said nothing as they descended further, the torchlight growing to glare into his eyes. He reflexively put up a hand to shield himself from the light, squinting at the figures holding them. Some wore hoods or heavy robes, while others wore more close-fitting attire, and others still (of the four-legged variety) elected to wear nothing. The few humans he could identify paused in hesitation. Silence rose about them, and Gaster stood quietly, his hands held at his sides.

The humans slowly departed, slipping away in single file. The remaining monsters circled about Gaster, the female skeleton leaving his side to take her place at the circle. The dark-skinned male with red hair that Gaster had seen on his first day in the glade asked, "Doctor, do you come in your interests, or is it in the interests of the crown?"

Gaster lowered his satchel from his shoulder to place upon the ground. Opening it, he withdrew the scroll. "Upon this are the official seals of the king and queen. You may look upon it at your leisure."

Pushing his ponytail out of the way, the male unfurled the scroll, and carefully read it. "Arawn?" The male with the blue hair, his companion at the fire, inquired from the opposite side of the circle.

Arawn nodded his head. "The seals are genuine." Passing the evidence on to the next monster in the circle, a female rabbit with a bracelet about her wrist that caught the torchlight, he said no more.

"Why send you here, alone? Surely it is not wise to leave you without a guard," a deer with wide, dark eyes, and massive horns inquired, stomping his foot against the ground a few times in agitation, "Is there someone hiding here?"

"No." Gaster took a step backward in surprise as the long-limbed monster, who had stared at him upon his early entry into the glade, swung down, and hung upside down, the torchlight reflected in the lenses of his eyes. "I could detect only him, and no others."

"Likely, then, Dughall, he has an ability to leave this glade immediately," the female skeleton noted.

Dughall nodded his head once, which made Gaster feel a little dizzy to watch, as he was still hanging upside down. "Precisely, yet he never brought any others with him."

"Is it fear of us, then, or is it perhaps a respect of our privacy, that is why you came alone?" A Whimsalot challenged. A Madjick snickered at that.

"We have committed no crimes against the crown. We wish only to be left alone to continue to practice our magic," the female rabbit added, waving her arm for emphasis, causing the bracelet on her wrist to glint.

Gaster knelt, and pulled his wooden tablets from his satchel. "I have documented my findings of your practices of magic for academic use."

"You did not ask permission," the female skeleton replied sharply, "You cloaked yourself within this forest, though we could detect you."

"You are citizens of this kingdom, all of you," Gaster replied, turning about, and indicating each assembled monster with his hand, "You enjoy the protections afforded to you by the king and queen."

"We have not broken any laws," a monster with two spiked horns replied in annoyance, folding his arms, "What gave you the right to take such notes? We have good reason to believe, then, that your intentions are less than legitimate."

Gaster nearly smirked at that, considering how the scroll was still being passed around. "I am an explorer, one that wishes to expand into a field that is little known by much of our society. I am merely chronicling your findings for others to know."

"We are not animals to be studied," Dugall hissed.

"But I have not studied you in that manner," Gaster defended himself, "I have only seen what you have allowed me to."

"Perhaps, then, we have allowed you to see too much as it is," the blue-haired man accused, "Those tablets belong to us."

"So, then, you are placing your own interests above those of the kingdom?" Gaster folded his hands together. "You have not been bothered by the crown, and have often been left to your own devices."

"What this seems to imply to me, then," a tall brown bear commented, "is that we are not trusted."

Gaster held out a hand. "When was the last time any of you shared your findings with the kingdom proper?" Silence greeted him, and he continued, "There have been no recorded findings from this glade over many years, despite the prowess of its magic users. What other choice was there, than to send in an explorer, one who, might I add, you yourselves have said was non-threatening?"

"Ideas are not objects of commerce," the horned monster replied sharply, "You haven't a right to them."

"No, of course not," Gaster replied smoothly, dropping his hand, "but they can be objects of politics. Communication with this area has been sparse."

"Silence does not indicate ill intent," the female skeleton replied in annoyance.

"No, but it does beg the question, considering how far flung your region is, and how you live among humans."

"Others do, as well!" The female rabbit cried in outrage.

"In more populated areas, yes," Gaster conceded, "thus, my point still stands."

"Guilty until proven innocent, then?" The bear growled.

"I am merely conducting research, and answering your questions accordingly. Note that the crown has heard nothing from you, despite making attempts at communication over the years."

"So, do you speak only for them, Doctor, or do you have a mind of your own?" Dughall commented, slowly spinning around in an inverted circle.

Gaster smirked. "They do place bread upon my table." The assembled circle laughed, and Gaster relaxed.

"I suppose that is to be expected. You wonder, then, why we remain on our own. Our knowledge is unfiltered," Arawn taunted, grinning, "Perhaps our minds are not so cluttered with the cares of the royal library."

The female rabbit's ears rose. "Do you think, perhaps, a re-education is in order?" At her words, Gaster's guard shot back up, and his hands switched, energy beneath them crackling as he began to build a shielding spell. This was immediately noticed by the rabbit, who waved her hand. "That was a joke."

"Have we come to a consensus, then?" Dughall asked with a yawn, "I grow bored of this."

The female skeleton was the first to speak. "He may monitor our magic, nothing more. I would also like for his notes to be checked."

"Would you be the one to monitor him, then, Ebrima, as he is the most similar to you in type?" The rabbit asked.

"Yes," her eyes narrowed, "but I would rather not babysit him." She turned her head to glance around, "Objections?"

Dughall shook his head. "No, I want this to end soon."

The Madjick shrugged, and the Whimsun replied, pointing at Gaster, "He must not forget his place."

"I do not want him whispering in the king and queen's ear how we live here!" The horned monster snarled.

Gaster narrowed his eye sockets. "You are not worth that type of attention, imp!"

The blue-haired man laughed. "Then we have little to fear. Nevertheless, Doctor, your skull would make a nice ornament, should you step out of line."

"And your head would make a beautiful decoration upon the pikes of a gate, should you murder the royal scientist," Gaster returned.

"Very well, then, no other objections?" Ebrima turned her head, her arms out. No one spoke, and she nodded her head. "I shall monitor you then, Doctor, but you had best not slow me down." She held up a finger. "One final stipulation." Gaster raised his head. "You must show us how you are able to enter and leave at will."

Gaster smirked, and raised his hands. "I think you were able to determine it already." Channeling his energy, he vanished.

Scrubbing the dirt off his bare bones, which glowed in the light of the moon through the high window, he felt the weight of the risk he was taking descending upon himself. Likely, if the inhabitants of the glade wanted him as a hostage, they could keep him, as they knew how he could come and go. Yet, at the same time, that hadn't happened. As for the human dwellers, if they wanted to keep him, would the monsters assist him, or see him as just a nuisance? He needed to learn more of their relationship with their neighbors. Then there was the mysterious Ebrima. While he was interested in the possibility of at last being able to track another monster's magic usage, he wondered what his relationship with her would be, and the exactitude of her magical prowess. Resting his shoulders against the back of the basin, he decided it would be best to meet with the royal guard again before departing.