After the barrier shattered, Sans waited anxiously. He could feel the magic leave him as the barrier crumbled entirely. Undyne cried out as he stumbled, falling to one knee with flurecent sweat beading his skull.
"What exactly was your plan here?!" She yelled, sprinting to support him. "Sans, those souls are the only reason you came back! I thought you knew something when you insisted on Asgore showing you the barrier but what in the hell is this?"
Sans hissed in pain, his pointed teethy manipulating into a thin smile. "Undyne... I know where she is... I could feel it... her leaving..." He huffed.
Undyne's expression slackened as she gasped. Mettaton looped an arm around the skeleton, pushing a snack into his hands. "Of course! That barrier is the most complex spell ever cast. If it took that many human souls to unwind it, no wonder you'd need to 'give' yourself into it to truly shatter it. In the moments you had it, you could sense its entirety couldn't you!"
Asgore growled. "How in the hell do you know so much about the barrier?"
Mettaton sighed dramatically. "Does it really matter? Sans, where is she? I'm able to contact Frisk and the others."
"She's..." Sans quieted as a shudder racked him. "She's angry. When she passed through the remains of the barrier it felt like pure animosity was ejecting from the Underground. It came from the Ruins."
Asgore flinched at the mention, a twinkle in his eyes. "She made it to the Ruins? It hasn't been that long... how did she... oh no... Toriel..."
Mettaton nodded, whipping out a familiar box and tapping away on it. Rei moved forward to steady Sans as Mettaton spoke on the phone. "What's the plan Sans..." Rei asked quietly. "You said she's angry, and came from the Ruins. We have shortcuts but there's no way we can get there that fast. You don't exactly look like you're gonna... Sans I don't know if you're going to survive."
He snarled quietly. Angrily he ripped open the packaged food he'd been handed and scarfed it down, replacing some of his HP. "I'll be fine. But you're right."
"She sure is..." Mettaton interjected. "Frisk and Toriel are in the Ruins now, but there isn't a way to get out that way safely. Dash said she'd be going as fast as possible to get them here but we need to move now. (Y/N) is a danger to herself and monsters alike in her current state."
"And humans!" Rei interjected. "She's on familiar soil now. She's angry, doesn't seem to have any memories, and I wouldn't be surprised if Chara is in her ear right now whispering."
Unlike Toriel's name, the mention of Chara seemed to visibly shake Asgore. He rocked back on his feet, looking at Rei with confusion and shock. "Chara? Where did you hear that name... you shouldn't know that name human..."
"Why? Do you know something about Chara? Something that could help?" Sans asked.
Asgore was quiet a second. He seemed lost as he thought, but shook his head. "More than likely, Toriel has already told you most everything. If you know her already...."
"Seriously? You can't tell us anything helpful about your own kid?" For what seemed like the first time, Undyne seemed genuinely disappointed with the king. Asgore glared at them bitterly, trying to mask his rage.
"Regardless of what my prior queen may tell you, that thing was not my child. My only child was taken from us because of Chara. That demon's obsession with revenge led them both to destruction. It's because of her my son... he..." Asgore's eyes didn't well with tears, but true remorse did infect his cruel face.
The group looked at him, a spread of reactions between them. Though there could be some pity for the bitter king, it didn't seem anyone could summon the will to comfort. Asgore stood quietly a moment. His brow furrowed before quietly he spoke again. "Chara, you said that she was in the Shifter's ear? What does that mean? Chara is supposed to have been dead for a very long time."
Sans looked Asgore uneasily. "Well, she's certainly still dead if that's what you mean. But some part of her still exists. At least her pain does... it's been a plague to the humans who've come down here."
His eyes widened slightly. "That damned brat..beast... of course she'd still haunt the Underground like the unsavory disea-"
"That's all well and good but we don't exactly has time to reminisce!" Rei cut him off. "Dash has collected Toriel and Frisk, she says she'll be here soon it seems. According to Frisk something definitely felt wrong. That original entrance must be where she escaped."
"Perfect! Your majesty, you should stay here and make sure the monsters stay safe." Undyne ordered. "We'll leave the barrier from here and work our way towards the entrance. Humans you'll need to lead us since we don't know much of anything about the surface."
Asgore scoffed. As he flexed a ginormous paw his crimson spear reappeared. "Captain, you forget your place. I will most certainly make a coward of myself staying here. I've already had my glory stolen."
"With all due respect sir, the underground can't lose a king. We can't-"
"You don't know where the entrance is Undyne. Nor do you know anything about Chara's home. I'll lead here."
Sans eyes widened. Stepping forward from the group. His steps seemed to carry more weight after the barrier broke. "Chara's home?"
The sound of hurried footsteps echoed in the halls. Collectively they turned to see as their missing numbers rejoined them. Papyrus and Toriel arrived atop what seemed to be a monstrous floating skull. Frisk was clinging to the back of Dash almost looking sick. As they came back into the room, Frisk stumbled from his perch, looking at Sans. "Sans! I'm so glad you're still here... without the other soul I'd thought..."
Sans kept his eyes on Asgore. His question lingered in the air. The king only smiled. "Sans is weak... but yes, his over indulgence in the souls hasn't killed him yet. Frustrating as it may be."
Asgore's eyes flickered up to Toriel. "I'm glad you were able to return as quickly as you have. I'm leading the charge. I strongly suspect we'll find our target nearest Chara's old village."
Toriel gasped quietly. Her scowl was telling against his smirk. You could almost hear him gloating despite the silence. Sans ignored the rivals, instead looking at his hands. As he flexed his fingers, it looked as though a faint copy of his limbs followed suit. His body buzzed with energy, but it felt as though he could shatter with the vibration.
Clenching a fist, he looked at Mettaton. "We can't all go. It's not safe. And if we fail... the Underground..." Sans trailed off. Shaking his head, he looked at Frisk and Toriel. "You need to stay here Toriel, and Frisk too. Tori you aren't much of a fighter anyway. Your defense is much stronger and that might just be what we need down here. And Frisk... we can't risk you getting killed. Not now."
Asgore snickered. "Oh, but there will be a time? How amusing..."
"Shut it!!" Sans voiced came out in a rough demand. "If it weren't for you we wouldn't be here."
Asgore went to argue but was silenced by Frisk's protest. "Sans, I can't stay here! I need to be there for her!" He begged.
Sans looked at him and smiled gently. Patting his head, he said "You will be. You'll be precisely where we need you. Trust me." The ominous tone of his words did nothing to quell the young child's fear, but the firm squeeze of Sans' hand seemed all Frisk needed. He nodded his head hesitantly.
From his pocket he pulled a phone, fidgeting with it. The contraption rattled loudly, beginning to morph. In seconds it looked to be a small clone of Mettaton's more simple form, still but familiar. Frisk thrust the box into Sans' hands. "Use this radio to keep in contact with us. It's like an earlier version of the phone Alphys gave us. But I can't miss a call, and neither can you. Keep us in the loop..."
Sans nodded solemnly. After lingering a moment, Frisk spun and ran to Toriel's side. Undyne and Mettaton were speaking with Asgore, discussing the battle plan. It seemed like all of the humans gathered around Toriel as well.
Sans stepped to join the leaving party, but a heavy boom shook the kingdom. They looked out through the shattered window as curtains of soil rained down from the ceiling. Almost faster than he could process, Undyne summoned and launched a spear. Sans couldn't make out the contact, but the explosion of small stone and dust was more than enough for explanation.
Asgore growled as he stomped towards the balcony. "What is that pest doing?" His stance was swollen and intimidating but Sans could hear a slight tremble in his tone.
Toriel stood beside him. "How did she... there's miles of space between her and the surface... How did she do that?"
Another crash reverberated in the cavern. This time instead of brief shouts and confused chatter, the remnants of the earlier crowd cried out in fear. Rogue stalagmites began to rain down, clouded by the accompanied showers of dirt to camouflaged their descent. In a blur Rei and Dash flew from the balcony, Rei held securely from her winged ally before launching herself towards one of the falling stones. She cried out as she struck the rock, a burst of stone signifying she'd obliterated her target.
Dash collected her again and they pursued their other targets. Toriel shouted for evacuation, summoning as many shields as she could and flinging them to cover the panicking monsters.
Mettaton seemed lost, listening for a moment before his expression became gaunt. "Your majesties, this seems like it's affecting as far out as the Waterfalls...."
Undyne shouted heroically, crushing another stone. "Dammit! We can't deal with this now."
Sans glanced between the groups, considering for a moment. Grunting, he stepped forward. His shoe caught on the flowers beneath him but he placed a hand on the King nonetheless. "Here's the plan. I'm taking the King with me to the surface. He and I can handle (Y/N), at least enough to get her to stop whatever this assault is. You all need to take care of the kingdom. Get to shelters, protect the monsters, stay safe."
"But Sans-"
"We're out of time!" He snapped violently. His voice was strained, angry and scared. As Sans looked at his companions they seemed speechless. They were unsure, stressed, and scared...
Sans' eyes moved to Frisk. The young boy trembled, but as they met gazed he offered a small smile. With a curt nod some semblance of reassurance washed over them. All of them. More crashing shook the Underground and they seemed to break silently. Undyne almost comically jumped from the window, her armor equipped and bright blueish magic embuing her entire being. The king looked at Sans and though he said nothing, he nodded.
Sans returned the gestured, tightening his grip on the King and giving a wry smile. "Hold tight." Sans warned.
Their surroundings morphed, blurring and humming. Unlike his usual teleportation the world seem to smear and transform, crystalline streaks of lights in every color consuming their surroundings. Asgore did his best to stay composed but the panic was clear on his face.
As the world came back, Sans felt like he was falling. He hadn't felt this way since he first discovered this power. The skeleton stumbled as they reappeared, catching himself on his knee. He opened his eyes again and his head was tilted down toward the Earth, small blade like vegetation reaching up towards him from the ground. His eyes widened, his palm pressing against the plants and twisting then between his boney digits.
"Grass..." He said. He'd seen grass before, but for whatever reason his felt different. It like behind him existed a void, and as he looked back he saw only the mouth a vast cave. Asgore laughed darkly, snapping in front of Sans face to get his attention.
"Welcome to the Surface..."
A loud boom, before a flash of tainted light lit the sky. Sans and Asgore both snapped to attention. A few seconds after, a strong gust of wind blew over them, almost strong enough to knock them over.
Sans squinted, but he couldn't see clear its source. He knew though. (Y/N) was there. Asgore pointed, grabbing onto Sans again. "Unless you can fly, I highly suggest you use that trick again and get us over there. The village is that way."
Energy buzzed within Sans. His breaths were uneven but it felt like his body was spilling over. A chorus of voices yelled in his head but despite the endless noise their excitement was clear. Sans nodded, grabbing the King again. "I can only really go places I've seen before, so let's hope this doesn't take to many trips. We need to find her fa-"
Two black tendrils curled against the sky. Like black ink was spilled across the sky before wriggling wildly. They wound and unwound themselves nonesenseically until from them formed two black chains. They hovered motionless before spinning rapidly. They tightened around one another, overlapping and spiraling until they appeared like a cocoon. From the chrysalis struck out violent blows, the chains crashing down on to earth. The same booming sounds repeated, growing faster. The waves of light and pure force washed over the two monsters in quick succession.
And then there she was...
She didn't look like her. Not Sans' version at any rate. But he knew it was her still. He furrowed his brow. The brimming magic within him burned as he forcibly grabbed the king. The world dissolved again, bringing them closer and closer.