The Royal Vow
An Adventure Time fanfiction
Summary; When Ice Queen returns after a five year absence, she brings along with her something that Prince Gumball had thought he'd never have to face again.
Notes; This is only my second AT fanfiction and the first one I've ever posted. I hope that you enjoy it!
Warnings: This story includes gay relationships. It's eventually going to become a very dark story, so please don't read it if you want to read something fluffy and cute. Thanks!

-Chapter 1 and junk-

Eighteen year old Fionna was an adventuress. She enjoyed spending her time fighting creatures, saving villages, and occasionally lounging around with her best friend, Cake. Her entire life was spent this way and she couldn't be happier, since she was doing what she loved.

Fionna lived in the land of Ooo. Over the years she had made (and lost) many friends and few enemies. But by far her favorite people (aside from Cake) were her best friend, Prince Gumball, and her boyfriend, Flame Prince.

"Yo, PG," She greeted as she entered the former's laboratory, while he pieced together some concoction. "What'cha makin'?"

"I'm attempting to put together a mighty potion to enhance a resistance to liquefying-" Prince Gumball, also known as PG, began to explain. However, after glancing at her confused face, he cleared his throat and began to make sense. "I'm trying to find out a way to make sugar more resistant to water."

"Fall in the lake again?" The girl grinned, taking a seat on her normal stool.

"Actually, no," He replied with a smile as he placed the beaker he was holding over a controlled flame. "Cinnamon Bun poured cocoa all over me and I nearly washed my hair away trying to get it out."

A laugh left the blonde haired girl's lips as she leaned back against the wall. "That sucks, dude! Good thing you didn't. I can't imagine you bald!"

Chuckling as she laughed, Gumball leaned in close and watched the liquid boil for a moment. "I actually called you here because I have a task for you."

"Yeah!" She chirped, grinning and sitting back up. "Sweet! What do I have to do?"

"Well," The Prince hummed as he removed the potion-in-progress from the heat. "It's been going around that someone saw the Ice Queen in her palace."

Fionna stared at him in surprise.

Now, you might not think it weird that a queen would be in her own palace, but there was a story behind it. The Ice Queen was a crazy woman who was known for kidnapping Princes in an attempt to get one to marry her. She had a habit of trying this at least once a week… or at least, she did about five years ago.

You see, one mysterious day when Fionna was almost 14, the Ice Queen had up and disappeared. Her entire palace had been emptied of her possessions. Even her penguins were gone.

Although they'd all been baffled by it, Prince Gumball had suggested that she had finally given up on trying to kidnap a Prince and moved away from the land of Ooo. Fionna wasn't so sure, but there wasn't much she could do about it at the time.

"Don't worry, BG!" The blonde-haired girl declared as she jumped to her feet, throwing a fist into the air into a mock-punch. "Cake and I are on it! ...As soon as I get her away from Mo-Cro."

Mo-Cro, or Lord Monochromicorn, was Cake's long-term boyfriend. They'd been going out since Fionna was young and Cake tried to spend as much time with him as she could.

The girl quickly bid farewell to the science-absorbed prince and left the castle to gather her best friend. Once Cake was (reluctantly) pulled away from her boyfriend, the two of them set off on the long trek toward the Ice Kingdom.

"But why would Ice Queen come back after all these years, I wonder?" Cake pondered as she walked, her rubber-like body stretched out to the size of a building as she walked across the plain.

"Maybe wherever she went kicked her out," Fionna snickered, before she snapped. "Ah, man! I should have brought Flame Prince along, he could threaten to melt her if she gets out of hand!"

"Knowing him, he'd cry as soon as one of her icicles touched him," Cake chuckled, earning a loud 'Hey!' from the human girl, only causing her to laugh louder. "Oh come on, Fi. You know he's a big baby about some things."

"Yeah, well… whatever," The girl huffed, crossing her arms over her chest. "You know," She sighed after a bit, leaning back to look up at the sky. "It's going to suck if Ice Queen really is back. PG was really able to focus more on having fun after she stopped kidnapping him all the time."

"Yeah, he was," Cake agreed thoughtfully. "He actually had some time off from being a Prince. It's too bad he didn't really get to spend it doing much."

A frown crossed Fionna's face, but she didn't respond.

"We're here," The stretchy cat informed as she placed her best friend on the ground, before shrinking back down to her normal size. "It still looks deserted to me."

"Nah, I think the candy kingdom is more dessert-ed," Fionna joked with a huge grin, earning a stare from the cat. "Get it? Dessert-ed?"

"I get it, Fi," Cake groaned as she turned and started up the long winding path toward the palace.

"Really?" The blonde whined, following after her friend. "I thought that one was good…"

The two of them made the walk up the mountain in good time and slowly approached the front opening, in case Ice Queen really was around. She was a ruthless lady and wouldn't hesitate to freeze them on sight if she saw them snooping around.

Neither of them were really surprised, however, when they saw no Ice Queen inside of the palace.

"Guess it was just a rumor," Fionna shrugged, turning to leave.

"Wait!" Cake cried, catching the blonde off guard. The cat crouched down and motioned for her human friend to follow suit, still looking inside.

"What?" The teenager questioned, looking around. She didn't see the woman anywhere, so what was the problem?

"What do you see, Fi?" Cake inquired, motioning inside.

"Nothing, dude," Fionna sighed. "Just Ice Quean's stuff and junk- wait!" Cake gave an approving noise as the girl threw a hand over her mouth. "Her stuff is here!"

"Which must mean that she's here!" Cake declared, turning to peer inside carefully.

They stared for a long time, but did not see the woman appear from any of the other rooms. Eventually they agreed and slowly ventured inside, glancing around carefully.

After checking the kitchen and the open bathroom door, it was obvious she wasn't there. But then Cake remembered something and perked her ears up.

"The mirror," She breathed, nodding toward a large mirror along the wall. "Remember? There's a secret room behind it."

"Oh yeah!" Fionna breathed, inching over toward it. She slipped her fingers between it and the wall of ice (nearly hissing at how cold it felt on her bare skin) and pulled it open a crack.

"See anything?" Her best friend inquired as the blonde-haired girl peeked inside.

"I don't see Ice Queen," The human replied, squinting through the darkness. "But… holy glob!" Cake nearly jumped out of her skin as the blonde gasped. "What is that!"

"What!" The cat cried in alarm. "What is what!"

Turning toward her best friend, Fionna looked at her with wide eyes. "There's a person in there!" Cake's own eyes went large and the blonde clenched her fists in front of her chest, her look turning to one of anger. "She probably brought some prince back with her or something!"

"Fi, wait-!" Cake cried as the girl turned to rush in. "We can't just grab him! What if Ice Queen put up traps?"

"Glob it!" The blonde hissed, turning to open the door a tiny bit more so that Cake could see. "We gotta think of a way to get him out of there."

Peering in, Cake took in the scene. Since she was a cat, she could see much better in the dark then Fionna could.

Just as the girl had said, there was a person inside of the room. He was seated in a chair made of ice, his body hunched somewhat forward and his unkempt dark hair covering most of his face. On top of his head was a golden crown with three red gems and his thin body was dressed in a gown that looked like something Prince Gumball would wear, but in blue.

The weirdest thing was that he wasn't chained down or looking for a way out… he was just… sitting there.

Fionna let out a noise of surprise and grabbed Cake, ducking behind a piece of furniture. The cat watched as with seconds to spare, the Ice Queen came storming in, a smile on her face and a plate of what looked like ice-cake in her hands.

"Oh sweetheart~!" She sing-songed, toeing open the mirror-door and slipping inside. "I brought you supper!"

As soon as the door was closing, the two adventuresses slipped over and stopped it with a crack open, peeping through curiously.

"You need to eat there, dearest," Ice Queen said to the boy as she reached out with her free hand, hooking one finger under his chin to lift it up. "Open wide!"

Cake and Fionna both watched with heavy stomachs as the woman fed the boy pieces of ice. He didn't give any response other than opening his mouth and swallowing it as it melted. When she was finished, his head hung once more.

"Are you liking our new place?" She inquired, motioning around them after placing the plate off to the side. "Or should I say, our old place?"

The boy let out a small noise, before he hoarsely breathed, "You broke… our deal."

The woman grinned widely and turned back toward him, her eyes narrowed. "Oh? Did I?"

"Stupid old bat…" The guy hissed. His voice was so strained that they could barely understand him. "You agreed that… that we wouldn't come back… if I married you…"

Cake reached up to throw a hand over Fionna's mouth as the girl gasped.

"Well, sweetheart," Ice Queen purred, lifting her left hand and shoving it in his face. The adventuresses could see a silver ring with a giant diamond around one of her fingers, shining in the dim light. "What are you going to do about it, hm? We're already married and you've already taken a Royal Vow!"

Fionna's eyebrows knitted in confusion. What was that? She'd never heard of it before… of course she'd heard of a Royal Promise, so she assumed this was similar. But still, she couldn't be sure until she asked PG.

"You old hag…" The boy groaned as he let his head fall again.

Ice Queen's triumphant face turned into one of anger and she held up her hand again, this time pointed at the boy. "I told you not to call me that!"

Fionna and Cake both couldn't hold in their sharp gasps this time as the boy let out a loud cry of pain, clutching his chest in pain.

The cat grabbed her friend's hand and bolted for the door. Fionna protested quietly and usually Cake would have agreed with her – they both hated running from fights – but as they slowed down at the bottom of the hill the feline stopped to explain.

"Fi!" She cried as she tried to calm the girl down. "Look- I have no idea with a 'Royal Vow' is, okay? But you saw what that witch did to him. If we barge in there and nab him, she'll just zap him again! Right?"

Letting out a frustrated huff, Fionna took a moment to breath and calm down, before she nodded. "Right…"

"So we need to go to Gumball and ask him about this Vow thing," Cake rationed. "Or else we could end up making a mistake and seriously hurting that kid."

With a heavy sigh, the blonde-haired girl gave a numb nod and reluctantly looked back at the ice palace. "Okay… but let's hurry."

Prince Gumball had been torn away from his failed experiment (it had ended up turning the sugar into rocks, instead of making it resist water…) for a meeting with his guardsmen. It hadn't taken long, but by the time it had finished he was tense and tired.

Still, when he spotted Fionna in the main entranceway he gave a warm smile and a wave. The sight of his friend always warmed his heart, even on his worst days.

This time, however, Fionna looked distraught. She rushed up to him and paused to catch her breath, which surprised the man. Usually she didn't do much running, what with Cake doing most of the walking, but it appeared as if she'd run part of the way herself.

"PG…!" The girl wheezed as Cake came running up beside her. "What is a Royal Vow!"

"Excuse me?" The Prince breathed, a little taken-aback by her appearance and the question.

"Please, just tell me!" Fionna begged, nearly in tears.

Gumball glanced down at Cake, who looked just as alarmed as her best friend. With a heavy breath, he cleared his throat and explained, "It's a wedding vow." The two girls gasped in horror, looking at each other, further raising his confusion. "Usually used in arranged marriages. The one who takes the vow pledges to do as the other wants and if the other person feels they are not… or, really, if they just feel like it… they can use magic to cause harm to them."

Fionna and Cake both looked at each other in absolute horror for a few moments, before the blonde-haired girl grabbed hold of the Prince's hands and clenched them tightly. "Is there any way to break it!"

"Well, it's not really like a Royal Promise," Gumball explained, frowning deeply in confusion. "You can't just… solve a math problem and make it go away, Fionna. But there is one way to break it. It's not easy, though."

"Tell me, please!" She begged, clenching his hand so tightly that he winced.

"Well," The Prince hummed, ready to see her disappointed face. "Love."

Fionna's face screwed into confusion as she bit her bottom lip. "Love?"

"Exactly," Gumball explained. "Someone has to love the captured person. Then they have to take the ring off of that person's finger. No one else can take it off."

"Oh glob, Cake!" The blonde-haired girl cried, turning toward her feline companion. "What do we do!"

"I don't know, sweetheart!" Cake declared, reaching her arms up to place them on Fionna's shoulders. "Give me a moment to think, alright?"

"Could you please explain to me what all this is about?" Gumball inquired, eyebrows knitting together in confusion.

As if he were a second thought, Fionna turned to him and quickly explained. "Ice Queen's got this guy in her secret room. He said that she promised not to come back to Ooo if he married her and she said he couldn't do anything about it because he'd taken a Royal Vow." She turned toward Cake once more, her eyes full of panic, before an idea occurred to her. "Wait! What if we sneak in there when Ice Queen's not around-"

"Fi-" Cake started, frowning.

"-Let me finish!" The girl declared, her voice high-pitched. "What if we sneak in there when Ice Queen's not around and ask that kid if he's got someone who loves him?"

The feline's eyes opened up for a moment before she thought about it. "That's… actually kind of a good idea."

"And if he does, we nab that person and bring them to him to take the ring off!" Cheering, Fionna pushed a fist into the air. "Yeah! That's gonna work, I just know it!"

"Fionna-" Prince Gumball attempted, but the girl was already running out with Cake on her heels. "Oh, glob… why do I think this is going to end badly?"

It took Ice Queen a good three hours to leave her palace again and as soon as she was gone, Fionna and Cake snuck inside. They approached the back room and quietly peaked inside for a few moments, surveying the scene. Then, as quietly as ninjas, they pushed open the door and slipped inside.

The guy was still seated, hunched over, in the chair made of ice. He was shivering and the closer they got, the more they realized that his body was not much more then skin and bones beneath his baggy, nearly see-through clothing.

Carefully, Fionna approached, her body tense and ready for any traps that might be sprung. But thankfully nothing happened and as she grew closer, he slowly lifted his eyes – though he kept his head down.

The boy let out a sharp, pained breath, his eyes widening slowly as the girl stepped into the light. Panic filled them as Cake followed her blonde best friend and slowly the boy leaned back, as if pulling away from them.

"It's okay!" Fionna declared, holding up her hands to show she meant no harm. "We're here to save you and junk."

"You need to go," He wheezed, grasping at the crown on his head and attempting to pull it down, over his face. "Just leave! You can't be here!"

"No, it's okay!" The blonde-haired girl cried, falling to her knees in front of him so she could look up at his face. "We know about the vow thing. We wanted to ask if there was anyone who loves you, who could break it? I mean like, because you can totally break it, dude! No worries. You just gotta tell us who loves you so we can get them to take off the ring!"

"No one loves me," The boy breathed in response, still hiding his face behind the crown and his mop of hair. "So just go!"

"No way, dude. Your parents at least have to love you, right?" Fionna asked as she reached out to grab the crown. He flinched away and reached out to stop her, but her hands grabbed hold of the golden ring before his weak arms could grab her. She pulled it away and gently reached out to brush his bangs out of his face, her smile gentle.

Then it fell and slowly twisted into a look of horror.

"M-Marshall Lee!"