(Btw this is long and also very inaccurate to the original Undertale game, I just kinda made up some cool stuff here so sorry if that bothers you lmao) 

You awoke groggily, the aftermaths of sleep still swimming behind your eyelids as you opened them, sitting up slowly and feeling your spine rearrange from your odd sleeping position.

You turned and noticed the empty space in the bed, and looked to the other side to see G sleeping soundly on the floor, covering in nothing but his clothes and you smiled as you reached down and shook him awake.

He jolted awake, grabbing your arm and pulling you down into the space on the floor beside him and you let out an 'oof' as you hit the floor.

He breathed heavily before turning to you, "Opal? Oh god, I'm so sorry. I just......I just had this dream." He turned his gaze towards the ceiling as his breathing slowed. "What dream?" You ask quietly, turning his face towards yours.

You see something dark, very dark flash in his eyes before he grins, pulling you both up off the floor and swings you onto his back as you wrap your legs around his ribs and yelp and he parades you out of the room on a piggy-back ride.

"G!" You squeal as he starts running down the hallway, making you wrap your arms around his neck and hold tight as he makes a sharp turn into the living room, throwing you down gently onto the couch as you laugh loudly.

Sans turns to you from the chair beside you, a smile making its way onto his face, "Welcome home, kiddo." He says, as Cyndle gets up from the chair beside him and helps you up off the couch.

"THE HUMAN IS AWAKE!" Papyrus said, quickly lifting you into the air as he yelled, "Papyrus put me down!" You said, laughing as he quickly apologized and placed you back on the floor.

All four of you laughed before a loud ring interrupted the joy, and you looked at Sans just as he looked at you, both of you sprinting up from the couch and towards the ringing phone.

You tripped him as he ran past you, laughing as you looked back before slamming into the kitchen counter, groaning and holding your stomach as you reached for the phone.

"This is Opal, badassery extraordinaire, how may I help you?" You mumbled, and the voice on the other end stuttered before answering, "Oh! Opal! It's Alphys, I was just calling to see if you were awake yet but....I guess you are if you're talking to me," She said, chuckling awkwardly as you smiled, "Damn Alphys, haven't heard your voice in a while, how are you and Undyne?" You asked, wiggling your eyebrows even thought she couldn't see you.

Alphys let out mumbles and stutters of embarrassment before yelling, "J-just have G run you down to the lab!" And you laughed as she hung up, as you set down the phone you turned to G, "So, I need to go to the lab?"

"Cause you're so hot." G said, pointing to your hands and chucking to himself, you gasped and turned to G, "Did you.....just make....a pun?" You asked, eyebrows raised as G suddenly realized what he had done, he suddenly got up and headed towards the door, "Alright people, Up! Let's go!" Sans and Cyndle nodded, "We'll stay here," Cyndle said, wiggling her eyebrows and blushing as you winked at her and Sans.

You threw on your snow boots and a scarf before trudging out into the snow, G throwing his arm around your shoulder as you stuck your tongue out to catch snowflakes, and G moved in to kiss you with this opportunity, but you smacked his arm away and pointed at him, "Nu uh, Ghost Rider, it ain't gonna be that easy, if you want," You ran your hands down your body and striked a pose, "This again."

G whined and grabbed your hips, pulling you closer to him, "Come on." He mumbled into your neck, "I'm sorry."

You pushed him away and swung your hips as you walked down the driveway, feeling his eyes on you as you smirked to yourself, "Coming?" You called back, throwing a sassy look at him over your shoulder as he quickly snapped out of it and ran after you.

~At The Lab~

"Alphys What's up?!" You called into the lab, throwing open the door as you flung your coat off and dropped it on the floor, Alphys poking her head out from behind a wall, smiling as she scuttered over to the two of you.

"H-hi!" She said, looking up at you and you smiled, bending down to her height, "I just h-have to run some tests on you, to see how your powers work and who they originally date back to, o-ok?" She said, and you nodded eagerly as G looked a little nervous, "This isn't gonna hurt her is it?" He said, and Alphys's grin dropped before it was thrown back on, "N-not at all!" She said, leading you into a room.

The walls were white and you looked forward as you noticed a glass screen in front of you, where Alphys and G were standing, watching you through the glass in what seemed to be a room full of gadgets and buttons.

"Are you ready?" Alphys called through a button in the room, and her voice could be heard over an intercom, you nodded, "Yeah sure....what exactly do I do-,"

You were interrupted as an ear piercing whine rang through your ears as you grabbed at your head, the sound feeling like it was ripping your skull apart, and as the noise numbed away you could feel something underneath your skin start to sizzle and boil.

"You said this wasn't gonna hurt her!" G yelled, leaning against the glass and eyeing your worriedly as you slowly got up from the ground, "The sound immediately activates powers, it was the only way!" Alphys said, looking towards G.

You stood tall, your brain still sizzling as you felt the boiling under your skin turn more and more toxic until your cried out in pain and held your wrists, your veins feeling like pure acid.

Alphys's eyes widened as she looked at the glowing green veins under your skin, "Something's wrong...," She whispered, as G turned to her, "What's wrong!? What's hurting her!?"

Alphys stared through the glass at you while she spoke, "Her powers have been pent up and smashed down for so long that they've built up to abnormal levels and now....," She turned to G, "She's more powerful that she ever had the potential to be."

Just as she said this, the acid inside your veins turned too strong to handle and fire burst from every inch of your body as it clouded the room, burning the walls and ceiling, and Alphys stared terrified looking through the glass as she couldn't see your figure through all the smoke and flame.

As the fire cleared, you stood in the middle of the room, looking down at your nails casually.

Both Alphys and G had confused looks on their faces as you looked up at them, and they gasped as they noticed your glowing red eyes, and the shining red veins under your skin, and you smiled as you said, "What's up guys?"

Alphys's mouth hung open in shock, but a ding rang out and her head turned as a machine next to her spit out a piece of paper, and she stared in silence at it, eyes wide.

"What?" G said, stepping closer and ripping the page out from Alphys's hands, and when he saw what was written he too stared at Opal in shock.

You sighed, "Cmon guys, what's the big deal? What does it even say?"

Alphys's stuttered as she took the paper back, pressing a button which made air ducts form in the room you were in, sucking all the fire and smoke away as you blinked, finally seeing clearly.

"Opal, you are....," Alphys rearranged her glasses on her nose, "Far more powerful than I ever thought."

You could feel the heat under your skin slowly draining as your furrowed your brows, "Well I know I'm super fucking badass, but you guys are kinda creeping me out."

Alphys motioned for you to come closer and you stepped out of the white room, stepping into the room full of gadgets as you took the paper.

"DNA results: Hybrid of the fire element, half human and half monster.

Heirs: Related to Ruby Cornelia Arthur, William Peter Arthur, Jackson and Daisy Arthur,"

The list of names went on, and you turned to Alphys with furrowed brows, "Those aren't my parents names....," You said slowly, "I don't even know these names."

"I'm not surprised." G said, "Ruby Arthur was the first ruler of the underground, about a thousand years ago, and that family held the bloodline of being the rulers for a long time, until Asgore and Toriel began ruling."

You scoffed, "That can't be right, I was born above ground, remember? I had parents." You said, and Alphys nodded, "That's correct, that's why I'm so shocked."

Alphas wiped her forehead, "Let's take some more tests."

~2 Hours Later~

You groaned as your eyes fluttered, "How many more times do I have to do this?" You said, your muscles straining as you did one last push up.

"There's DNA in your sweat, which is why we need you to this." Alphys said, as the machine next to her spit out the paper again and she threw it onto the pile she already had, frustrated, "They all say the same thing!"

You sighed, letting yourself fall from the bar, your muscles finally relaxing as your breathed heavily.

G looked at you through the glass and sighed, "Alphys," He said, "I think the tests are right."

Alphys looked up at him and sent the signal for you to come back into the room, and you walked slowly, sweating as you took the paper again, "This dosent make sense." You said, out of breath.

Alphys took her glasses off and rubbed her temples before speaking, "Opal.....," She said, "You might be the original heir to the Underground."

///YO WASSUP GUYS PLOT TWIST///