The wind blew, humming an ominous tune. A familiar tune. The light shifted, growing brighter before simmering in a tranquil wave.
Standing there for as long as he had made the entire experience feel surreal, like this was his world. His entire reality one of shifting light, an endless vortex of nothing.

The barrier stood tall, it was an opponent that many before had faced and failed to take down. This was the enemy, so many had suffered because of.
And here he stood, a short, punny skeleton wearing an old blue jumper, carrying the hope of monster kind on his shoulders.

Everyone questioning, was he going to be the final opponent? The victor of this ongoing battle. Would he set them all free?

"is everything ready?" Sans asks, looking over his shoulder. A yellow dinosaur lady stood looking like a tangled ball of nerves.

"Y-Yes, everything... everything is set, every-everyone is packed and waiting out-outside." Alphys answers with her usual stutter, Sans nods. "Are-Are you s-sure you're ready-y? I know we-we've been over th-this but this t-task will be- exhausting an-and straining. With-With the state your soul is in-"

"my stats don't play into this anymore, al. i have the equivalent of a human and monster soul, i'll be fine." Sans turns to his friend, his smile sitting as a reassuring grin. Alphys nods, not in confidence but in understanding. Even if he wasn't fine afterwards, if he dies during this, she knew he wouldn't have it any other way. They all knew the risks, and they'd accepted them. Sans was willing to give his life for this, death didn't scare him.
He'd said a single thing about it, a final convincing statement.

"the fear of death is the most unjustified of all fears, for there's no risk of accident for someone who's dead."

Both Asgore and Alphys knew that they wouldn't be able to stop him, the best they could do was be there to save him if necessary.
Sans had done many things, planned ahead and even enlisted the help of one of the best healers monsterkind had ever had. Queen Toriel.
The queen had come with both Sans and another monster by the name of Flowey, a monster Alphys recognized.
At first, she'd tried to ask questions, but she held her tongue.
Asgore, however, was a trainwreck, I mean, you would probably be in the same state if someone, who you'd thought to be dead had suddenly just turned up with one of your trusted colleagues. (Like the feeling of your dad not coming home with the milk and finding him years later at your boss's house.)
Still, he put a brave face on and muddled through. All the family drama could wait because, with Flowey present, there was going to be a heck of a lot more.

"Doctor Alphys, Sans, are we ready?" Asgore asks, entering the room.

"yep, ready as we'll ever be." Sans hums, Alphys nods meekly.

"Excellent, shall we begin?" Asgore speaks, Sans stretches, his bones pop and crack. Alphys and Asgore step back as Sans shakes his hands. Shake the nerves out.

"alright, let's do this."

Sans pulls his soul out, the crimson heart sat in front of his chest, red erupting around the heart. He chuffs out a deep breath, his hands cup around his soul, the red hue twirls and surrounds his hands. The red hue turned from a hazy glow to dense, Sans' hands disappeared within the crimson.
If he could describe how he felt, he'd say his brain felt like scrambled eggs, and his body felt like shit on the windscreen of a burning car. If he were to compare his experience to something someone else felt, he'd say how Dabi felt when he lost his jaw but worse.
The white light of the barrier changed into a shifting red, the room filled with new light. Then the haze focused on a point, bleeping into the barrier. Cracks and dents form in the seemingly intangible wall as the energy concentrates on a spot, opening up.
Green patches appear, they begin to spread and open until you can see to the other side.

Grass.

"get everyone moving!" Sans shouts, Asgore scurry off, returning moments later with all of monster kind following him. Asgore walks up to his side. "remember who to look out for." Sans hums, Asgore nods.

"Let us leave this underground prison! Together!" Asgore shouts to the crowd, they cheer back before rushing past. Asgore led the way, everyone besides Sans and Toriel hung back.

"SANS!" Papyrus shouts, latching onto his brother.

"tryin' to keep it steady ain't easy when you're latched onto me like this." Sans hums, Papyrus lets go.

"Didn't think you had it in ya, punk!" Undyne shouts, smiling down at the shorter skeleton.

"yeah, well, surprise." Sans shrugs. "now, it'd be best if you all went through with the others. go enjoy the surface, and i'll meet you on the other side."

"WHAT? WITHOUT YOU?" Papyrus asks.

"everyone has to go through before me because once i'm through, the- barrier will become unstable and close again. i'll be with you before you can say bones."

"ARE YOU SURE, BROTHER?" Papyrus, despite his loud voice, was concerned. Maybe even a little scared.

"Come on, punk! If anything, your bro is the only person who couldn't get trapped behind!" Undyne slaps Papyrus' shoulder. Papyrus looks back to the portal before nodding.

"ALRIGHT, BROTHER, I SHALL SEE YOU ON THE OTHER SIDE! NYEHEHE!" He shouts, running off into the sun.

"You better make it punk!" Undyne shouts, following after him. Sans couldn't help but laugh at his brothers antics. It took a few minutes for all the monsters to filter through, and by that point, Sans just wanted to curl up in a corner and sleep.

"go ahead, i've got one more thing i need to do." Sans hums, Toriel raises an eyebrow. "trust me, i'll make it through." With that small amount of convincing, Toriel nods, stepping through to join her subjects. "alright flowey, c'mon." Sans releases one of his hands, offering it to the empty space to his side. Flowey pops up and latches onto his forearm. "you ready?"

"Are you gonna hold up your end of the deal? Or, more realistically, can you?" Flowey looked on at the skeleton suspiciously.

"i can, i'm sure of it." Sans hums, turning to the portal and walking forward. "The surface awaits."

"I wish Chara was here." Flowey's words come out as only a whisper, if he wasn't sitting on his arm, Sans doubts he would've heard it.

A/N:
Hello! So, Monster Kind is finally on the surface. Or so it seems... :)
Hope you all enjoyed the chapter! Only a few to go, it almost doesn't feel real!